Interface Commands

This chapter contains the commands used to configure nonprotocol-specific interface features. For hardware technical descriptions, and for information about installing the router interfaces, refer to the hardware installation and maintenance publication for your particular product.

For interface configuration tasks and examples, refer to the chapter entitled "Configuring Interfaces" in the Router Products Configuration Guide.

For information about the Channel Interface Processor (CIP), see the chapter entitled "IBM Channel Attach Commands." The CIP is described in a separate chapter because of the interrelationship of host system configuration values and router configuration values.

access-list (standard)

Use the access-list global configuration command to establish MAC address access lists. Use the no form of this command to remove a single access list entry.

Syntax Description

Default

No MAC address access lists are established.

Command Mode

Global configuration

Related Commands

access-list (type-code)

access-list (type-code)

Use the access-list global configuration command to build type-code access lists. Use the no form of this command to remove a single access list entry.

Syntax Description

Default

No type-code access lists are built.

Command Mode

Global configuration

Usage Guidelines

Type-code access lists can have an impact on system performance; therefore, keep the lists as short as possible and use wildcard bit masks whenever possible.

Access lists are evaluated according to the following algorithm:

• If the packet is Ethernet Type II or SNAP, the type-code field is used.

• Other packet type, then the LSAP is used.

If the length/type field is greater than 1500, the packet is treated as an LSAP packet unless the DSAP and SSAP fields are AAAA. If the latter is true, the packet is treated using type-code filtering.

If you have both Ethernet Type II and LSAP packets on your network, you should set up access lists for both.

Use the last item of an access list to specify a default action; for example, permit everything else or deny everything else. If nothing else in the access list matches, the default action is normally to deny access; that is, filter out all other type codes.

Related Commands

access-list (extended)
access-list (standard)

async default ip address

To assign the interface address that is used by the device connecting to the router via PPP or SLIP, unless you override the address at the command line, use the async default ip address interface configuration command. Use the no form of this command to remove the address from your configuration.

Syntax Description

Default

No interface address is assigned.

Command Mode

Interface configuration

Example

The following example specifies address 182.32.7.51 on asynchronous interface 1:

interface async 1
async default ip address 182.32.7.51

Related Command

async dynamic address

async dynamic address

To specify an address on an asynchronous interface (rather than using the default address), use the async dynamic address interface configuration command. Use the no form of this command to disable dynamic addressing.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Example

The following example shows dynamic addressing assigned to an interface:

interface async 1
async dynamic address

Related Commands

ppp
slip

async dynamic routing

To implement asynchronous routing on an interface, use the async dynamic routing interface configuration command. The no form of this command disables use of routing protocols; static routing will still be used.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Example

The following example shows how to enable asynchronous routing on asynchronous interface 1. The ip tcp header-compression passive command enables Van Jacobson TCP header compression and prevents transmission of compressed packets until a compressed packet arrives from the asynchronous link.

interface async 1
async dynamic routing
async dynamic address
async default ip address 1.1.1.2
ip tcp header-compression passive

Related Commands

A dagger (⁺) indicates that the command is documented in another chapter.

async dynamic address
ip tcp header-compression ⁺

async mode dedicated

To place a line into network mode using SLIP or PPP encapsulation, use the async mode dedicated interface configuration command. The no form of this command returns the line to interactive mode.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

With dedicated asynchronous mode, the interface will use either SLIP or PPP encapsulation, depending on which encapsulation method is configured for the interface. An EXEC prompt does not appear, and the line is not available for normal interactive use.

Example

The following example assigns an Internet address to an asynchronous line and places the line into network mode. Setting the stop bits to 1 enhances performance.

interface async 1
async default ip address 182.32.7.51
async mode dedicated
encapsulation slip

Related Command

async mode interactive

async mode interactive

To enable the slip and ppp EXEC commands, use the async mode interactive line configuration command. Use the no form of this command to prevent users from implementing SLIP and PPP at the EXEC level.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Example

The following example enables the ppp and slip EXEC commands:

interface async 1
async mode interactive

Related Commands

async mode dedicated
ppp
slip

auto-polarity

To enable automatic receiver polarity reversal on a hub port connected to an Ethernet interface of a Cisco 2505 or Cisco 2507, use the auto-polarity hub configuration command. To disable this feature, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Default

Enabled

Command Mode

Hub configuration

Usage Guidelines

This command applies to a port on an Ethernet hub only.

Example

The following example enables automatic receiver polarity reversal on hub 0, ports 1 through 3:

hub ethernet 0 1 3
auto-polarity

Related Command

hub

backup delay

To define how much time should elapse before a secondary line is set up or taken down after a primary line transition, use the backup delay interface configuration command. Use the no form of this command to remove the definition.

Syntax Description

Default

never

Command Mode

Interface configuration

Usage Guidelines

When a primary line goes down, the router delays the amount of seconds defined by the enable-delay argument before enabling the secondary line. If, after the delay period, the primary line is still down, the secondary line is activated.

When a primary line comes back up, the router will delay the amount of seconds defined by the disable-delay argument.

Examples

The following example sets a 10-second delay on deactivating the secondary line; however, the line is activated immediately:

interface serial 0
backup delay 0 10

The same example on the Cisco 7000 requires the following commands:

interface serial 1/1
backup delay 0 10

backup interface serial

To configure the serial interface as a secondary, or dial backup line, use the backup interface serial interface configuration command. Use the no form of this command with the appropriate serial port designation to turn disable this feature.

Syntax Description

Default

Disabled

Command Mode

Interface configuration

Examples

The following example sets serial 1 as the backup line to serial 0:

interface serial 0
backup interface serial 1

The following example on the Cisco 7000 sets serial 2 as the backup line to serial 1:

interface serial 1/1
backup interface serial 2/2

Related Command

down-when-looped

backup load

To set the traffic load thresholds for dial backup service, use the backup load interface configuration command. Use the no form of this command to remove the setting.

Syntax Description

Default

Both arguments default to never.

Command Mode

Interface configuration

Usage Guidelines

When the transmitted or received load on the primary line is greater than the value assigned to the enable-threshold argument, the secondary line is enabled.

When the transmitted load on the primary line plus the transmitted load on the secondary line is less than the value entered for the disable-load argument, and the received load on the primary line plus the received load on the secondary line is less than the value entered for the disable-load argument, the secondary line is disabled.

If the never keyword is used instead of an enable-threshold value, the secondary line is never activated because of load. If the never keyword is used instead of a disable-load value, the secondary line is never deactivated because of load.

Examples

The following example sets the traffic load threshold to 60 percent on the primary line. When that load is exceeded, the secondary line is activated, and will not be deactivated until the combined load is less than 5 percent of the primary bandwidth.

interface serial 0
backup load 60 5

The same example on the Cisco 7000 requires the following commands:

interface serial 1/1
backup load 60 5

bandwidth

To set a bandwidth value for an interface, use the bandwidth interface configuration command. Use the no form of this command to restore the default values.

Syntax Description

Default

Default bandwidth values are set during startup and can be displayed with the EXEC command show interfaces.

Command Mode

Interface configuration

Usage Guidelines

The bandwidth command sets an informational parameter only; you cannot adjust the actual bandwidth of an interface with this command. For some media, such as Ethernet, the bandwidth is fixed; for other media, such as serial lines, you can change the actual bandwidth by adjusting hardware. For both classes of media, you can use the bandwidth configuration command to communicate the current bandwidth to the higher-level protocols.

Example

The following example sets the full bandwidth for DS3 transmissions:

interface serial 0
bandwidth 44736

Related Command

A dagger (⁺) indicates that the command is documented in another chapter.

vines metric ⁺

channel-group

Use the channel-group controller configuration command to define the timeslots that belong to each T1 or E1 circuit.

Syntax Description

Default

The default line speed when configuring a T1 controller is 56 kbps.

The default line speed when configuring an E1 controller is 64 kbps.

Command Mode

Controller configuration

Usage Guidelines

Use this command in configurations where the router is intended to communicate with a T1 or E1 fractional data line. The channel-group number may be arbitrarily assigned and must be unique for the controller. The timeslot range must match the timeslots assigned to the channel group. The service provider defines the timeslots that comprise a channel group.

Example

In the following example, three channel groups are defined. Channel-group 0 consists of a single timeslot, channel-group 8 consists of 7 timeslots and runs at a speed of 64 kbps per timeslot, and channel-group 12 consists of a single timeslot.

channel-group 0 timeslots 1
channel-group 8 timeslots 5,7,12-15,20 speed 64
channel-group 12 timeslots 2

Related Commands

linecode
framing

clear controller

Use the clear controller EXEC command to reset the T1 or E1 controller interface on the Cisco 7000 series or Cisco 4000 series routers.

Syntax Description

Command Mode

EXEC

Examples

The following example resets the T1 controller at slot 4, port 0 on a Cisco 7000 series router:

clear controller t1 4/0

The following example resets the E1 controller at NIM 0 on a Cisco 4000 series router:

clear controller e1 0

Related Command

controller e1
controller t1

clear controller lex

To reboot the LAN Extender chassis and restart its operating software, use the clear controller lex privileged EXEC command.

Syntax Description

Command Mode

Privileged EXEC

Usage Guidelines

The clear controller lex command halts operation of the LAN Extender and performs a cold restart.

Without the prom keyword, if an image exists in Flash memory, and that image has a newer software version than the PROM image, and that image has a valid checksum, then this command runs the Flash image. If any one of these three conditions is not met, this command reloads the PROM image.

With the prom keyword, this command reloads the PROM image, regardless of any Flash image.

Examples

The following example halts operation of the LAN Extender bound to LAN Extender interface 2 and causes the LAN Extender to perform a cold restart from Flash memory:

Router# clear controller lex 2
reload remote lex controller? [confirm] yes

The following example halts operation of the LAN Extender bound to LAN Extender interface 2 and causes the LAN Extender to perform a cold restart from PROM:

Router# clear controller lex 2 prom
reload remote lex controller? [confirm] yes

clear counters

To clear the interface counters, use the clear counters EXEC command.

Syntax Description

Command Mode

EXEC

Usage Guidelines

This command clears all the current interface counters from the interface unless the optional arguments type and number are specified to clear only a specific interface type (serial, Ethernet, Token Ring, and so on).

Examples

The following example illustrates how to clear all interface counters:

clear counters

The following example illustrates how to clear interface counters on the serial interface residing on a Cisco 1000 series LAN Extender:

clear counters lex 0 serial

Related Command

show interfaces

clear hub

To reset and reinitialize the hub hardware connected to an interface of a Cisco 2505 or Cisco 2507, use the clear hub ethernet EXEC command.

Syntax Description

Command Mode

EXEC

Example

The following example clears hub 0:

clear hub ethernet 0

Related Command

hub

clear hub counters

To set to zero the hub counters on an interface of a Cisco 2505 or Cisco 2507, use the clear hub counters EXEC command.

Syntax Description

Command Mode

EXEC

Example

The following example clears the counters displayed in a show hub command for all ports on hub 0:

clear hub counters ether 0

Related Command

show hub

clear interface

To reset the hardware logic on an interface, use the clear interface EXEC command.

Syntax Description

Command Mode

EXEC

Usage Guidelines

Under normal circumstances, you do not need to clear the hardware logic on interfaces.

Example

The following example resets the interface logic on HSSI interface 1:

clear interface hssi 1

clear rif-cache

To clear entries from the Routing Information Field (RIF) cache, use the clear rif-cache EXEC command.

Syntax Description

This command has no arguments or keywords.

Command Mode

EXEC

Example

The following example illustrates how to clear the RIF cache:

clear rif-cache

Related Command

A dagger (⁺) indicates that the command is documented in another chapter.

multiring ⁺

clear service-module

To reset the CSU/DSU, use the clear service-module privileged EXEC configuration command.

Syntax Description

Default

None

Command Mode

Privileged EXEC

Usage Guidelines

Use this command only in severe circumstances (for example, when the router is not responding to a CSU/DSU configuration command).

This command terminates all DTE and line loopbacks that are locally or remotely configured. It also interrupts data transmission through the router for up to 15 seconds.

The CSU/DSU module is not reset with the clear interface command.

Related Commands

clear counters
test service-module

clock rate

To configure the clock rate for the hardware connections on the serial interface appliques, network interface modules (NIMs), and interface processors (IPs) to an acceptable bit rate, use the clock rate interface configuration command. Use the no clock rate command to remove the clock rate if you change the interface from a DCE to a DTE device.

Syntax Description

Default

No clock rate is configured.

Command Mode

Interface configuration

Usage Guidelines

Be aware that the fastest speeds might not work if your cable is too long, and that speeds faster than 148,000 bits per second are too fast for RS-232 signaling. It is recommended that you only use the synchronous serial RS-232 signal at speeds up to 64,000 bits per second. To permit a faster speed, use an RS-449 or V.35 applique.

Example

The following example sets the clock rate on the first serial interface to 64,000 bits per second:

interface serial 0
clock rate 64000

clock source (controller)

Use the clock source controller configuration command to set the T1-line clock-source for the MIP in the Cisco 7000 or for the NIM in the Cisco 4000.

Syntax Description

Default

T1 line

Command Mode

Controller configuration

Usage Guidelines

This command is used in configurations where the interfaces are connected back-to-back, rather than to a T1 line, and one of the interfaces must provide a clocking signal. When the interface is connected to a channelized T1 line, this command need never be used.

Example

The following example enables internal clocking:

clock source internal

Related Commands

framing
linecode

clock source (interface)

To control which clock a G.703-E1 interface will use to clock its transmitted data from, use the clock source interface configuration command. The no form of this command restores the default value.

Syntax Description

Default

By default, the applique uses the line's receive data stream.

Command Mode

Interface configuration

Usage Guidelines

This command applies to a Cisco 4000 router or Cisco 7000 series router. A G.703-E1 interface can clock its transmitted data from either its internal clock or from a clock recovered from the line's receive data stream.

Example

The following example specifies the G.703-E1 interface to clock its transmitted data from its internal clock:

clock source internal

cmt connect

To start the processes that perform the connection management (CMT) function and allow the ring on one fiber to be started, use the cmt connect EXEC command.

Syntax Description

Command Mode

EXEC

Usage Guidelines

In normal operation, the FDDI interface is operational once the interface is connected and configured. The cmt connect command allows the operator to start the processes that perform the CMT function.

Examples

The following examples demonstrate use of the cmt connect command for starting the CMT processes on the FDDI ring.

The following command starts all FDDI interfaces:

cmt connect

The following command starts both fibers on the FDDI interface unit zero:

cmt connect fddi 0

The following command on the Cisco 7000 starts both fibers on the FDDI interface unit zero:

cmt connect fddi 1/0

The following command starts only Physical Sublayer A on the FDDI interface unit 0 (zero):

cmt connect fddi 0 phy-a

The following command on the Cisco 7000 starts only Physical Sublayer A on the FDDI interface unit 0 (zero):

cmt connect fddi 1/0 phy-a

cmt disconnect

To stop the processes that perform the connection management (CMT) function and allow the ring on one fiber to be stopped, use the cmt disconnect EXEC command.

Syntax Description

Command Mode

EXEC

Usage Guidelines

In normal operation, the FDDI interface is operational once the interface is connected and configured, and is turned off using the shutdown interface configuration command. The cmt disconnect command allows the operator to stop the processes that perform the CMT function and allow the ring on one fiber to be stopped.

The cmt disconnect command is not needed in the normal operation of FDDI; this command is used mainly in interoperability tests.

Examples

The following examples demonstrate use of the cmt disconnect command for stopping the CMT processes on the FDDI ring.

The following command stops all FDDI interfaces:

cmt disconnect

The following command stops both fibers on the FDDI interface unit zero:

cmt disconnect fddi 0

The following command on the Cisco 7000 stops both fibers on the FDDI interface unit zero:

cmt disconnect fddi 1/0

The following command stops only Physical Sublayer A on the FDDI interface unit 0 (zero). This command causes the FDDI media to go into a wrapped state so that the ring will be broken.

cmt disconnect fddi 0 phy-a

The following command on the Cisco 7000 stops only Physical Sublayer A on the FDDI interface unit 0 (zero). This command causes the FDDI media to go into a wrapped state so that the ring will be broken.

cmt disconnect fddi 1/0 phy-a

compress

To configure software compression for Link Access Procedure, Balanced (LAPB), Point-to-Point Protocol (PPP), and High-Level Data Link Control (HDLC) encapsulations, use the compress interface configuration command. To disable compression, use the no form of this command.

Syntax Description

Default

Compression is disabled.

Command Mode

Interface configuration

Usage Guidelines

You can configure point-to-point software compression for all LAPB, PPP, and HDLC encapsulations. Compression reduces the size of frames via lossless data compression. The compression algorithm used is a predictor algorithm (the RAND compression algorithm), which uses a compression dictionary to predict what the next character in the frame will be.

Table 6-3 provides general guidelines for deciding which compression type to select for LAPB encapsulations.

Examples

The following example enables predictor compression on serial interface 0 for a LAPB link:

interface serial 0
encapsulation lapb
compress predictor
mtu 1509
lapb n1 12072

The following example enables Stacker compression on serial interface 0 for a LAPB link. This example does not set the MTU size and the maximum bits per frame (N1); we recommend that you do not change those LAPB parameters for Stacker compression:

interface serial 0
encapsulation lapb
compress predictor

Related Commands

A dagger (⁺) indicates that the command is documented in another chapter.

encapsulation lapb
encapsulation x25
show compress
show processes ⁺

controller

To configure a T1 or E1 controller and enter controller configuration mode, use the controller global configuration command.

Syntax Description

Default

No T1 or E1 controller is configured.

Command Mode

Global configuration

Usage Guidelines

This command is used in configurations where the router is intended to communicate with a T1 or E1 fractional data line. Additional parameters for the T1 or E1 line must be configured for the controller before the T1 or E1 circuits can be configured by means of the interface global configuration command.

Example

In the following example, the MIP in slot 4, port 0 of a Cisco 7000 is configured as a T1 controller:

controller t1 4/0

In the following example, NIM 0 of a Cisco 4000 is configured as a T1 controller:

controller t1 0

Related Commands

channel-group
clear controller lex
clear controller t1
clock source (controller)
framing
linecode
show controllers e1
show controller t1

copy flash lex

To download an executable image from Flash memory on the core router to the LAN Extender chassis, use the copy flash lex privileged EXEC command.

Syntax Description

Command Mode

Privileged EXEC

Usage Guidelines

If you attempt to download a version of the software older than what is currently running on the LAN Extender, a warning message is displayed.

Example

The following example illustrates how to copy the executable image namexx to the LAN Extender interface 0:

Router# copy flash lex 0
Name of file to copy? namexx
Address of remote host [255.255.255.255] <cr>
writing namexx !!!!!!!!!!!!!!!!!!!!!!!!!copy complete

Related Command

copy tftp lex

copy tftp lex

To download an executable image from a TFTP server to the LAN Extender, use the copy tftp lex privileged EXEC command.

Syntax Description

Command Mode

Privileged EXEC

Usage Guidelines

If you attempt to download a version of the software older than what is currently running on the LAN Extender, a warning message is displayed.

Example

The following example illustrates how to copy the file namexx from the TFTP server:

Router# copy tftp lex 0
Address or name of remote host (255.255.255.255]? 131.108.1.111
Name of file to copy? namexx
OK to overwrite software version 1.0 with 1.1 ?[confirm]
Loading namexx from 131.108.13.111!!!!!!!!!!!!!!!!!!!!!!!!!
[OK - 127825/131072 bytes]
Successful download to LAN Extender

crc

To set the length of the cyclic redundancy check (CRC) on a Fast Serial Interface Processor (FSIP) or HSSI Interface Processor (HIP) of the Cisco 7000 series only, use the crc interface configuration command. To set the CRC length to 16 bits, use the no form of this command.

Syntax Description

Default

16 bits

Command Mode

Interface configuration

Usage Guidelines

All interfaces use a 16-bit cyclic redundancy check (CRC) by default, but also support a 32-bit CRC. CRC is an error-checking technique that uses a calculated numeric value to detect errors in transmitted data. The designators 16 and 32 indicate the length (in bits) of the frame check sequence (FCS). A CRC of 32 bits provides more powerful error detection, but adds overhead. Both the sender and receiver must use the same setting.

CRC-16, the most widely used throughout the United States and Europe, is used extensively with wide-area networks (WANs). CRC-32 is specified by IEEE 802 and as an option by some point-to-point transmission standards. It is often used on SMDS networks and LANs.

Example

In the following example, the 32-bit CRC is enabled on serial interface 3/0:

interface serial 3/0
crc 32

crc4

To enable generation of the G.703-E1 CRC4, use the crc4 interface configuration command. To disable this feature, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

This command applies to a Cisco 4000 router or Cisco 7000 series router. It is useful for checking data integrity while operating in framed mode. CRC4 provides additional protection for a frame alignment signal under noisy conditions. Refer to CCITT Recommendation G.704 for a definition of CRC4.

Example

The following example enables CRC4 generation on the G.703-E1 interface:

crc4

dce-terminal-timing enable

When running the line at high speeds and long distances, use the dce-terminal-timing enable interface configuration command to prevent phase shifting of the data with respect to the clock. If SCTE is not available from the DTE, use no form of this command, which causes the DCE to use its own clock instead of SCTE from the DTE.

Syntax Description

This command has no keywords or arguments.

Default

DCE uses its own clock.

Command Mode

Interface configuration

Usage Guidelines

On the Cisco 4000 platform, you can specify the serial Network Interface Module timing signal configuration. When the board is operating as a DCE and the DTE provides terminal timing (SCTE or TT), the dce-terminal-timing enable command causes the DCE to use SCTE from the DTE.

Example

The following example prevents phase shifting of the data with respect to the clock:

interface serial 0
dce-terminal-timing enable

delay

To set a delay value for an interface, use the delay interface configuration command. Use the no form of this command to restore the default delay value.

Syntax Description

Default

Default delay values may be displayed with the EXEC command show interfaces.

Command Mode

Interface configuration

Example

The following example sets a 30,000-microsecond delay on serial interface 3:

interface serial 3
delay 30000

Related Command

show interfaces

description (controller)

To add a description to an E1 or T1 controller interface on a Cisco 7000 series router, use the description controller configuration command. Use the no form of this command to remove the description.

Syntax Description

Default

No description is added.

Command Mode

Controller configuration

Usage Guidelines

The description command is meant solely as a comment to be put in the configuration to help you remember what certain E1 or T1 controllers are used for. The description affects the MIP interfaces only and appears in the output of the show controllers e1, show controllers t1, and show running-config EXEC commands.

Example

The following example shows how to add a description for a T1 controller on slot 4, port 1, channel group 0:

interface serial 4/1:0
description Fractional T1 line to Mountain View -- 128 Kb/s

Related Commands

A dagger (⁺) indicates that the command is documented in another chapter.

show controllers e1
show controller t1
show running-config⁺

description (interface)

To add a description to an interface configuration, use the description interface configuration command. Use the no form of this command to remove the description.

Syntax Description

Default

No description is added.

Command Mode

Interface configuration

Usage Guidelines

The description command is meant solely as a comment to be put in the configuration to help you remember what certain interfaces are used for. The description appears in the output of the following EXEC commands: show startup-config, show interfaces, and show running-config.

Example

The following example describes a 3174 controller on serial interface 0:

interface serial 0
description 3174 Controller for test lab

Related Commands

A dagger (⁺) indicates that the command is documented in another chapter.

show interfaces
show running-config ⁺
show startup-config ⁺

down-when-looped

To configure an interface to inform the system it is down when loopback is detected, use the down-when-looped interface configuration command.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

This command is valid for HDLC or PPP encapsulation on serial and HSSI interfaces.

When an interface has a backup interface configured, it is often desirable that the backup interface be enabled when the primary interface is either down or in loopback. By default, the backup is only enabled if the primary interface is down. By using the down-when-looped command, the backup interface will also be enabled if the primary interface is in loopback.

If testing an interface with the loopback command, or by placing the DCE into loopback, down-when-looped should not be configured; otherwise, packets will not be transmitted out the interface that is being tested.

Example

In the following example, interface serial 0 is configured for HDLC encapsulation. It is then configured to let the system know that it is down when in loopback mode.

interface serial0
encapsulation hdlc
down-when-looped

Related Commands

backup interface serial
loopback (interface)

dte-invert-txc

On the Cisco 4000 platform, you can specify the serial Network Interface Module timing signal configuration. When the board is operating as a DTE, the dte-invert-txc command inverts the TXC clock signal it gets from the DCE that the DTE uses to transmit data. Use the no form of this command if the DCE accepts SCTE from the DTE.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

Use this command if the DCE cannot receive SCTE from the DTE, the data is running at high speeds, and the transmission line is long. This prevents phase shifting of the data with respect to the clock.

If the DCE accepts SCTE from the DTE, use no dte-invert-txc.

Example

The following example inverts the TXC on serial interface 0:

interface serial 0
dte-invert-txc

early-token-release

To enable early token release, use the early-token-release interface configuration command. Once enabled, use the no form of this command to disable this feature.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

Early token release is a method whereby the Token Ring interfaces can release the token back onto the ring immediately after transmitting, rather than waiting for the frame to return. This feature helps increase the total bandwidth of the Token Ring.

The CSC-C2CTR, CSC-R16 (or CSC-R16M), CSC-2R, and CSC-1R cards and the Token Ring Interface Processor (TRIP) on the Cisco 7000 all support early token release.

Examples

The following example enables the use of early token release on Token Ring interface 1:

interface tokenring 1
early-token-release

On the Cisco 7000 series, to enable the use of early token release on your Token Ring interface processor in slot 4 on port 1, issue the following configuration commands:

interface tokenring 4/1
early-token-release

encapsulation

To set the encapsulation method used by the interface, use the encapsulation interface configuration command.

Syntax Description

Default

The default depends on the type of interface. For example, a synchronous serial interface defaults to HDLC.

Command Mode

Interface configuration

Usage Guidelines

In order to use SLIP or PPP, the router must be configured with an IP routing protocol or with the ip host-routing command. This configuration is done automatically if you are using old-style slip address commands. However, you must configure it manually if you configure SLIP or PPP via the interface async command.

Examples

The following example resets HDLC serial encapsulation on serial interface 1:

interface serial 1
encapsulation hdlc

The following example enables PPP encapsulation on serial interface 0:

interface serial 0
encapsulation ppp

Related Commands

keepalive
ppp
ppp authentication
slip

encapsulation atm-dxi

Use the encapsulation atm-dxi interface configuration command to enable ATM-DXI encapsulation. The no form of this command disables ATM-DXI.

Syntax Description

This command has no arguments or keywords.

Default

HDLC

Command Mode

Interface configuration

Example

The following example configures ATM-DXI encapsulation on serial interface 1:

interface serial 1
encapsulation atm-dxi

Related Command

atm-dxi map

encapsulation lapb

To set the LAPB encapsulation method used by the interface, use the encapsulation lapb interface configuration command.

Syntax Description

Default

DTE is the default operational type.

IP is the default protocol type.

Command Mode

Interface configuration

Usage Guidelines

In order to use a particular encapsulation, you must configure the router with that protocol type.

Example

The following example enables LAPB encapsulation on serial interface 0, using a default IP routing protocol:

interface serial 0
encapsulation lapb

encapsulation x25

To specify an serial interface's operation as an X.25 device, use the encapsulation x25 interface configuration command.

Syntax Description

Defaults

The default serial encapsulation is HDLC. You must explicitly configure an X.25 encapsulation method.

DTE operation is the default X.25 mode. Cisco's traditional X.25 encapsulation method is the default.

Command Mode

Interface configuration

Usage Guidelines

One end of an X.25 link must be a logical DCE and the other end a logical DTE. (This assignment is independent of the interface's hardware DTE/DCE identity.) Typically, when connecting to a public data network (PDN), the customer equipment acts as the DTE and the PDN attachment acts as the DCE.

Cisco has supported the encapsulation of a number of datagram protocols for quite some time, using a standard means when available and proprietary means when necessary. More recently the IETF adopted a standard, RFC 1356, for encapsulating most types of datagram traffic over X.25. X.25 interfaces use Cisco's traditional method unless explicitly configured for IETF operation; if the ietf keyword is specified, that standard will be used unless Cisco's traditional method is explicitly configured. For details see the x25 map command.

When an X.25 interface is reconfigured, all of the interface's X.25 parameters are initialized except the x25 map commands. The x25 map statements that are configured for an interface are not deleted when the encapsulation is changed, so they will be retained if the interface is later reconfigured for X.25 operation.

A router attaching to the Defense Data Network (DDN) or to a Blacker Front End (BFE) device can be configured to use their respective algorithms to convert between IP and X.121 addresses by using the ddn or bfe options, respectively. An IP address should be assigned to the interface, from which the algorithm will generate the interface's X.121 address; for proper operation, this X.121 address should not be modified.

A router DDN attachment can operate as either a DTE or a DCE device. A BFE attachment can operate only as a DTE device. The ietf option is not available if either the ddn or bfe option is selected.

Example

The following example configures the interface for connection to a Blacker Front End device:

interface serial 0
encapsulation x25 bfe

fddi burst-count

To allow the FCI card to preallocate buffers to handle bursty FDDI traffic (for example, NFS bursty traffic), use the fddi burst-count interface configuration command. Use the no form of this command to revert to the default value.

Syntax Description

Default

3 buffers

Command Mode

Interface configuration

Usage Guidelines

This command applies to the FCI card only. The microcode software version should not be 128.45 or 128.43.

Example

The following example sets the number of buffers to 5:

interface fddi 0
fddi burst-count 5

fddi c-min

To set the C-Min timer on the PCM, use the fddi c-min interface configuration command. Use the no form of this command to revert to the default value.

Syntax Description

Default

1600 microseconds

Command Mode

Interface configuration

Usage Guidelines

This command applies to the processor CMT only. You need extensive knowledge of the PCM state machine to tune this timer. Use this command when you run into PCM interoperability problems.

Example

The following example sets the C-Min timer to 2000 microseconds:

interface fddi 0
fddi c-min 2000

Related Commands

fddi tb-min
fddi tl-min-time
fddi t-out

fddi cmt-signal-bits

To control the information transmitted during the connection management (CMT) signaling phase, use the fddi cmt-signal-bits interface configuration command.

Syntax Description

Defaults

The default signal bits for the phy-a and phy-b keywords are as follows:

• phy-a is set to 0x008 (hexadecimal) or 00 0000 1000 (binary). Bits 1 and 2 are set to 00 to select Physical A. Bit 3 is set to 1 to indicate "accept any connection."

• phy-b is set to 0x20c (hexadecimal) or 10 0000 1100 (binary). Bits 1 and 2 are set to 10 to select Physical B. Bit 3 is set to 1 to indicate "accept any connection." Bit 9 is set to 1 to select MAC on output. The normal data flow on FDDI is input on Physical A and output on Physical B.

Command Mode

Interface configuration

Usage Guidelines

If neither the phy-a nor phy-b keyword is specified, the signal bits apply to both physical connections.

Use Table 6-6 and Table 6-7 to set the physical type and duration bits.

Example

The following example sets the CMT signaling phase to signal bits 0x208 on both physical connections:

interface fddi 0
fddi cmt-signal-bits 208

fddi duplicate-address-check

To turn on the duplicate address detection capability on the FDDI, use the fddi duplicate-address-check interface configuration command. Use the no form of this command to disable this feature.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

This command is used only to check duplicate addresses before and during ring initialization. Even without this command, the software checks for duplicate addresses after the ring is up and operational.

If you use this command, the router will detect a duplicate address if multiple stations are sharing the same MAC address. If the router finds a duplicate address, it will shut down the interface.

Example

The following example enables duplicate address checking on the FDDI:

interface fddi 0
fddi duplicate-address-check

fddi encapsulate

To specify encapsulating bridge mode on the CSC-C2/FCIT interface card, use the fddi encapsulate interface configuration command. Use the no form of this command to turn off encapsulation bridging and return the FCIT interface to its translational, nonencapsulating mode.

Syntax Description

This command has no arguments or keywords.

Default

The FDDI interface by default uses the SNAP encapsulation format defined in RFC 1042. It is not necessary to define an encapsulation method for this interface when using the CSC-FCI interface card.

Command Mode

Interface configuration

Usage Guidelines

The no fddi encapsulate command applies only to CSC-C2/FCIT interfaces, because the CSC-FCI interfaces are always in encapsulating bridge mode.The CSC-C2/FCIT interface card fully supports transparent and translational bridging for the following configurations:

• FDDI to FDDI

• FDDI to Ethernet

• FDDI to Token Ring

The command fddi encapsulate puts the CSC-C2/FCIT interface into encapsulation mode when doing bridging. In transparent mode, the FCIT interface interoperates with earlier versions of the CSC-FCI encapsulating interfaces when performing bridging functions on the same ring.

 
Caution Bridging between dissimilar media presents several problems that can prevent communications from occurring. These problems include bit-order translation (or usage of MAC addresses as data), maximum transfer unit (MTU) differences, frame status differences, and multicast address usage. Some or all of these problems might be present in a multimedia bridged LAN and might prevent communication from taking place. These problems are most prevalent when bridging between Token Rings and Ethernets or between Token Rings and FDDI nets. This is because of the different way Token Ring is implemented by the end nodes.

The following protocols have problems when bridged between Token Ring and other media: Novell IPX, DECnet Phase IV, AppleTalk, VINES, XNS, and IP. Further, the following protocols may have problems when bridged between FDDI and other media: Novell IPX and XNS. We recommend that these protocols be routed whenever possible.

Example

The following example sets FDDI interface 1 on the CSC-C2/FCIT interface card to encapsulating bridge mode:

interface fddi 1
fddi encapsulate

fddi smt-frames

To enable the SMT frame processing capability on the FDDI, use the fddi smt-frames interface configuration command. Use the no form of this command to disable this feature, in which case the router will not generate or respond to SMT frames.

Syntax Description

This command has no arguments or keywords.

Default

Enabled

Command Mode

Interface configuration

Usage Guidelines

Use the no form of this command to turn off SMT frame processing for diagnosing purposes. Use the fddi smt-frames command to reenable the feature.

Example

The following example disables SMT frame processing:

interface fddi 0
no fddi smt-frames

fddi tb-min

To set the TB-Min timer in the physical connection management (PCM), use the fddi tb-min interface configuration command. Use the no form of this command to revert to the default value.

Syntax Description

Default

100 milliseconds

Command Mode

Interface configuration

Usage Guidelines

This command applies to the processor CMT only. You need extensive knowledge of the PCM state machine to tune this timer. Use this command when you run into PCM interoperability problems.

Example

The following example sets the TB-Min timer to 200 milliseconds:

interface fddi 0
fddi tb-min 200

Related Commands

fddi c-min
fddi tl-min-time
fddi t-out

fddi tl-min-time

To control the TL-Min time (the minimum time to transmit a Physical Sublayer, or PHY line state, before advancing to the next physical connection management (PCM) state, as defined by the X3T9.5 specification), use the fddi tl-min-time interface configuration command.

Syntax Description

Default

30 microseconds

Command Mode

Interface configuration

Usage Guidelines

Interoperability tests have shown that some implementations of the FDDI standard need more than 30 microseconds to sense a signal.

Examples

The following example changes the TL-Min time from 30 microseconds to 100 microseconds:

interface fddi 0
fddi tl-min-time 100

The following example changes the TL-Min time from 30 microseconds to 100 microseconds on a Cisco 7000:

interface fddi 3/0
fddi tl-min-time 100

Related Commands

fddi c-min
fddi tl-min-time
fddi t-out

fddi token-rotation-time

To control ring scheduling during normal operation and to detect and recover from serious ring error situations, use the fddi token-rotation-time interface configuration command.

Syntax Description

Default

5000 microseconds

Command Mode

Interface configuration

Usage Guidelines

The FDDI standard restricts the allowed time to be greater than 4000 microseconds and less than 165,000 microseconds. As defined in the X3T9.5 specification, the value remaining in the TRT is loaded into the token holding timer (THT). Combining the values of these two timers provides the means to determine the amount of bandwidth available for subsequent transmissions.

Examples

The following example sets the rotation time to 24,000 microseconds:

interface fddi 0
fddi token-rotation-time 24000

The following example sets the rotation time to 24,000 microseconds on a Cisco 7000:

interface fddi 3/0
fddi token-rotation-time 24000

fddi t-out

To set the t-out timer in the physical connection management (PCM), use the fddi t-out interface configuration command. Use the no form of this command to revert to the default value.

Syntax Description

Default

100 milliseconds

Command Mode

Interface configuration

Usage Guidelines

This command applies to the processor CMT only. You need extensive knowledge of the PCM state machine to tune this timer. Use this command when you run into PCM interoperability problems.

Example

The following example sets the timeout timer to 200 milliseconds:

interface fddi 0
fddi t-out 200

Related Commands

fddi c-min
fddi tb-min
fddi tl-min-time

fddi valid-transmission-time

To recover from a transient ring error, use the fddi valid-transmission-time interface configuration command.

Syntax Description

Default

2500 microseconds

Command Mode

Interface configuration

Examples

The following example changes the transmission timer interval to 3000 microseconds:

interface fddi 0
fddi valid-transmission-time 3000

The following example changes the transmission timer interval to 3000 microseconds on a
Cisco 7000:

interface fddi 3/0
fddi valid-transmission-time 3000

framing

Use the framing controller configuration command to select the frame type for the T1 or E1 data line.

Syntax Description

Defaults

Super frame is the default on a T1 line.

CRC4 frame is the default on an E1 line.

Command Mode

Controller configuration

Usage Guidelines

Use this command in configurations where the router is intended to communicate with T1 or E1 fractional data line. The service provider determines which framing type, either sf, esf, or crc4 is required for your T1/E1 circuit.

Example

The following example selects extended super frame as the T1 frame type:

framing esf

Related Commands

channel-group
linecode

full-duplex

Use the full-duplex interface configuration command to specify full-duplex mode on a Fast Ethernet Interface Processor (FEIP) port or on a serial interface port that uses bisynchronous tunneling. Use the no form of this command to restore the default half-duplex mode.

Syntax Description

This command has no arguments or keywords.

Default

Half-duplex mode is the default mode on a Cisco 7000 series router with a FEIP.

Half-duplex mode is the default mode is the default mode for serial interfaces that are configured for bisynchronous tunneling.

Command Mode

Interface configuration

Usage Guidelines

Use this command if your equipment on the other end is capable of full-duplex mode.

Example

The following example configures full duplex mode on the Cisco 7000:

interface fastethernet 0/1
full-duplex

The following example specifies full-duplex binary synchronous communications (BSC) mode:

interface serial 0
encapsulation bstun
full-duplex

Related Command

interface fastethernet

group-range

To create a list of member asynchronous interfaces (associated with a group interface), use the group-range command. Use the no form of the command to remove an interface from the member list.

Syntax Description

Default

No interfaces are designated as members of a group.

Command Mode

Interface configuration

Usage Guidelines

Using the group-range command, you create a group of asynchronous interfaces that are associated with a group asynchronous interface on the same device. This group interface is configured by using the interface group-async command. This one-to-many structure allows you to configure all associated member interfaces by entering one command on the group interface, rather than entering this command on each interface. You can customize the configuration on a specific interface by using the member command.

Examples

The following example defines interfaces 2, 3, 4, 5, 6, and 7 as members of asynchronous group interface 0:

interface group-async 0
group range 2 7 

Related Commands

interface group-async
member

half-duplex

Use the half-duplex interface configuration command to configure an SDLC interface for half-duplex mode.Use the no form of this command to reset the interface for full-duplex mode.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

The half-duplex command is used to configure an SDLC interface for half-duplex mode.

The half-duplex command deprecates the both the sdlc hdx and media-type half-duplex commands.

Example

In the following example, an SDLC interface has been configured for half-duplex mode:

encapsulation sdlc-primary
half-duplex

Related Commands

half-duplex timer

half-duplex controlled-carrier

To place a low-speed serial interface in controlled-carrier mode, instead of constant-carrier mode, use the half-duplex controlled-carrier interface configuration command. Use the no form of this command to return the interface to constant-carrier mode.

Syntax Description

This command has no arguments or keywords.

Default

Constant-carrier mode, where DCD is held constant and asserted by the DCE half-duplex interface.

Command Mode

Interface Configuration

Usage Guidelines

This command applies only to low-speed serial DCE interfaces in half-duplex mode. Configure a serial interface for half-duplex mode by using the half-duplex command. These interfaces are available on Cisco 2520 through 2523 routers.

Controlled-carrier operation means that the DCE interface will have DCD de-asserted in the quiescent state. When the interface has something to transmit, it will assert DCD, wait a user-configured amount of time, then start the transmission. When the interface has finished transmitting, it will again wait a user configured amount of time, then deassert DCD.

An interface placed in controlled-carrier mode can be returned to constant-carrier mode by using the no form of the command.

Examples

The following examples show how to place the interface in controlled-carrier mode and back into constant-carrier operation.

Changing to controlled-carrier mode from the default of constant-carrier operation:

Router(config)# interface serial 2
Router(config-if)# half-duplex controlled-carrier

Changing to constant-carrier operation from controlled-carrier mode:

Router(config)# interface serial 2
Router(config-if)# no half-duplex controlled-carrier

Related Commands

half-duplex timer
physical-layer

half-duplex timer

To tune half-duplex timers, use the half-duplex timer interface configuration command. The half-duplex timer cts-delay command replaces the sdlc cts-delay command. The half-duplex timer rts-timeout command replaces the sdlc rts-timeout command. Use the no form of this command, along with the appropriate keyword, to return to the default value for that parameter.

You can configure more than one of these options, but each option must be specified as a separate command.

Syntax Description

Default

The default cts-delay value is 0 ms.

The default cts-drop-timeout value is 250 ms.

The default dcd-drop-delay value is 100 ms.

The default dcd-txstart-delay value is 100 ms.

The default rts-drop-delay value is 3 ms.

The default rts-timeout value is 3 ms.

The default transmit-delay value is 0 ms.

Command Mode

Interface configuration

Usage Guidelines

The half-duplex timer command is used to tune half-duplex timers. These timer tuning commands permit you to adjust the timing of the half-duplex state machines to suit the particular needs of their half-duplex installation.

The range of values for the cts-delay and rts-timeout keywords are dependent on the serial interface hardware.

Examples

The following examples show how to set the cts-delay timer to 10 ms and the transmit-delay timer to 50 ms.

Cobra(config)# interface serial 2
Cobra(config-if)# half-duplex timer cts-delay 10
Cobra(config-if)# half-duplex timer transmit-delay 50

Related Commands

half-duplex controlled-carrier
physical-layer

hold-queue

To specify the hold-queue limit of an interface, use the hold-queue interface configuration command. Use the no form of this command with the appropriate keyword to restore the default values for an interface.

Syntax Description

Default

The default input hold-queue limit is 75 packets. The default output hold-queue limit is 40 packets. These limits prevent a malfunctioning interface from consuming an excessive amount of memory. There is no fixed upper limit to a queue size.

Command Mode

Interface configuration

Usage Guidelines

The input hold queue prevents a single interface from flooding the network server with too many input packets. Further input packets are discarded if the interface has too many input packets outstanding in the system.

If priority output queueing is being used, the length of the four output queues is set using the priority-list global configuration command. The hold-queue command cannot be used to set an output hold queue length in this situation.

For slow links, use a small output hold-queue limit. This approach prevents storing packets at a rate that exceeds the transmission capability of the link. For fast links, use a large output hold-queue limit. A fast link may be busy for a short time (and thus require the hold queue), but can empty the output hold queue quickly when capacity returns.

To display the current hold queue setting and the number of packets discarded because of hold queue overflows, use the EXEC command show interfaces.

Example

The following example illustrates how to set a small input queue on a slow serial line:

interface serial 0
hold-queue 30 in

Related Command

show interfaces

hssi external-loop-request

To allow the router to support a CSU/DSU that uses the LC signal to request a loopback from the router, use the hssi external-loop-request interface configuration command. Use the no form of this command to disable the feature.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

The HSA applique (on the HSSI) contains an LED that indicates the LA, LB, and LC signals transiting through the devices. The CSU/DSU uses the LC signal to request a loopback from the router. The CSU/DSU may want to do this so that its own network management diagnostics can independently check the integrity of the connection between the CSU/DSU and the router.

Use this command to enable a two-way, internal, and external loopback request on HSSI from the CSU/DSU.

Example

The following example enables a CSU/DSU to use the LC signal to request a loopback from the router:

hssi external-loop-request

hssi internal-clock

To convert the HSSI interface into a 45 MHz clock master, use the hssi internal-clock interface configuration command. Use the no form of this command to disable the clock master mode.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

Use this command in conjunction with the HSSI null-modem cable to connect two Cisco routers together with HSSI. You must configure this command at both ends of the link, not just one.

Example

The following example converts the HSSI interface into a 45 MHz clock master:

hssi internal-clock

hub

To enable and configure a port on an Ethernet hub of a Cisco 2505 or Cisco 2507, use the hub global configuration command.

Syntax Description

Default

No hub ports are configured.

Command Mode

Global configuration

Examples

The following example enables port 1 on hub 0:

hub ethernet 0 1
no shutdown

The following example enables ports 1 through 8 on hub 0:

hub ethernet 0 1 8
no shutdown

Related Command

shutdown

ignore-dcd

Use the ignore-dcd interface configuration command to configure the serial interface to monitor the DSR signal (instead of the DCD signal) as the line up/down indicator. Use the no form of this command to restore the default behavior.

Syntax Description

This command has no arguments or keywords.

Default

The serial interface, operating in DTE mode, monitors the DCD signal as the line up/down indicator.

Command Mode

Interface configuration

Usage Guidelines

This command applies to Quad Serial NIM interfaces on the Cisco 4000 series and Hitachi-based serial interfaces on the Cisco 2500 series and Cisco 3000 series.

When the serial interface is operating in DTE mode, it monitors the Data Carrier Detect (DCD) signal as the line up/down indicator. By default, the attached DCE device sends the DCD signal. When the DTE interface detects the DCD signal, it changes the state of the interface to up.

In some configurations, such as an SDLC multidrop environment, the DCE device sends the Data Set Ready (DSR) signal instead of the DCD signal, which prevents the interface from coming up. Use this command to tell the interface to monitor the DSR signal instead of the DCD signal as the line up/down indicator.

Example

The following example configures serial interface 0 to monitor the DSR signal as the line up/down indicator:

interface serial 0
ignore-dcd

interface

To configure an interface type and enter interface configuration mode, use the interface global configuration command.

To configure a subinterface, use the interface global configuration command.

Syntax Description

Default

None

Command Mode

Global configuration

Usage Guidelines

Subinterfaces can be configured to support partially meshed Frame Relay networks (refer to the chapter entitled "Configuring Interfaces" in the Router Products Configuration Guide).

Examples

In the following example, serial interface 0 is configured with PPP encapsulation:

interface serial 0
encapsulation ppp

The following example enables loopback mode and assigns an IP network address and network mask to the interface. The loopback interface established here will always appear to be up:

interface loopback 0
ip address 131.108.1.1 255.255.255.0

The following example for the Cisco 7000 shows the interface configuration command for Ethernet port 4 on the EIP that is installed in (or recently removed from) slot 2:

interface ethernet 2/4

The following example begins configuration on the Token Ring interface processor in slot 1 on
port 0 of a Cisco 7000:

interface tokenring 1/0

The following example shows how a partially meshed Frame Relay network can be configured. In this example, subinterface serial 0.1 is configured as a multipoint subinterface with three frame relay PVCs associated, and subinterface serial 0.2 is configured as a point-to-point subinterface.

interface serial 0
encapsulation frame-relay
interface serial 0.1 multipoint
ip address 131.108.10.1 255.255.255.0
frame-relay interface-dlci 42 broadcast
frame-relay interface-dlci 53 broadcast
interface serial 0.2 point-to-point
ip address 131.108.11.1 255.255.0
frame-relay interface-dlci 59 broadcast

controller t1 4/1
circuit 0 1
interface serial 4/1:0
ip address 131.108.13.1 255.255.255.0
encapsulation ppp

interface lex 0

Related Commands

A dagger (⁺) indicates that the command is documented in another chapter.

circuit
controller
mac-address ⁺
ppp
show interfaces
slip

interface group-async

To create a group interface that will serve as master, to which asynchronous interfaces can be associated as members, use the interface group-async command. Use the no form of the command to restore the default.

Syntax Description

Default

No interfaces are designated as group masters.

Command Mode

Global configuration

Usage Guidelines

Using the interface group-async command, you create a single asynchronous interface to which other interfaces are associated as members using the group-range command. This one-to-many configuration allows you to configure all associated member interfaces by entering one command on the group master interface, rather than entering this command on each individual interface. You can create multiple group masters on a device; however, each member interface can only be associated with one group.

Examples

The following example defines asynchronous group master interface 0:

interface group-async 0

Related Commands

group-range
member

invert-transmit-clock

Delays between the SCTE clock and data transmission indicate that the transmit clock signal might not be appropriate for the interface rate and length of cable being used. Different ends of the wire may have variances that differ slightly. To invert the clock signal to compensate for these factors, use the invert-transmit-clock interface configuration command. This command applies only to the Cisco 7000 series. To return to the transmit clock signal to its initial state, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Command Mode

Interface configuration

Example

In the following example, the clock signal on serial interface 3/0 is inverted.

interface serial 3/0
invert-transmit-clock

ip address-pool

To enable the global default address-pooling mechanism used to supply IP addresses on dial-in asynchronous, synchronous, or ISDN point-to-point interfaces, use the ip address-pool global configuration command. To disable IP address pooling globally on all interfaces with the default configuration, use the no form of the command.

Syntax Description

Default

IP address pooling is disabled.

Command Mode

Global configuration

Usage Guidelines

The Global Default Mechanism applies to all interfaces that have been left in their default setting of peer default ip address pool.

If any peer default ip address command (other than peer default ip address pool, the default) is configured, then the interface uses that mechanism and not the Global Default Mechanism. Thus all interfaces can be independently configured or left unconfigured so that the Global Default Mechanism setting will apply. This flexibility minimizes the configuration effort on the part of the administrator.

Examples

The following example specifies the DHCP proxy client mechanism as the Global Default Mechanism for assigning peer IP addresses:

ip address-pool dhcp-proxy-client

The following example specifies a local IP address pool called default as the Global Default Mechanism for all interfaces that are left in the default setting:

ip address-pool local

Related Commands

A dagger (⁺) indicates that the command is documented in another chapter.

encapsulation ppp
encapsulation slip
ip dhcp-server
ip local pool
member peer default ip address
peer default ip address
peer default ip address pool
ppp⁺
show dhcp
show ip local pool
slip ⁺

ip dhcp-server

To specify which Dynamic Host Configuration Protocol (DHCP) servers to use on your network, specify the IP address of one or more DHCP servers available on the network by using the ip dhcp-server global configuration command. Use the no form of the command to remove a DHCP server's IP address.

Syntax Description

Default

The IP limited broadcast address of 255.255.255.255 is used for transactions if no DHCP server is specified. This allows autodetection of DHCP servers.

Command Mode

Global configuration

Usage Guidelines

You can specify up to ten servers on the network.

A DHCP server temporarily allocates network addresses to clients through the access server on an as-needed basis. While the client is active, the address is automatically renewed in a minimum of 20-minute increments. When the user terminates the session, the interface connection is terminated so that network resources can be quickly reused.

In normal situations, if a user's SLIP/PPP session fails (for example if a modem line disconnects), the allocated address will be reserved temporarily to preserve the same IP address for the client when dialed back into the server. This way, the session that was accidentally terminated can often be resumed.

To use the DHCP proxy-client feature, enable your access server to be a proxy-client on asynchronous interfaces by using the ip address-pool dhcp-proxy-client command. If you wish to specify which DHCP servers are used on your network, use the ip dhcp-server command to define up to ten specific DHCP servers.

The ip address-pool dhcp-proxy-client command initializes proxy-client status to all interfaces defined as asynchronous on the access server. To selectively disable proxy-client status on a single asynchronous interface, use the no peer default ip address interface command.

Example

The following command specifies a DHCP server with the IP address of 129.12.13.81:

ip dhcp-server 129.12.13.81

Related Commands

A dagger (⁺) indicates that the command is documented in another chapter.

ip address-pool dhcp-proxy-client
ip helper address ⁺
peer default ip address pool
show dhcp⁺

ip local pool

To configure a local pool of IP addresses to be used when a remote peer connects to a point-to-point interface, use the ip local pool global configuration command. To delete an address pool, use the no form of this command.

Syntax Description

Default

No address pools are preconfigured.

Command Mode

Global configuration

Usage Guidelines

Use the ip local pool command to create one or more local address pools from which IP addresses are assigned when a peer connects. The default address pool is then used on all point-to-point interfaces after the ip address-pool local global configuration command has been issued. To use a specific named address pool on an interface, use the peer default ip address pool interface configuration command.

These pools can also be used with the translate command for one-step VTY asynchronous connections and in certain AAA/TACACS+ authorization functions. Refer to the chapters "Protocol Translation" and "System Management" of the Access and Communication Configuration Guide for more information. Pools can be displayed with the show ip local pool command.

Example

The following command creates a local IP address pool by the name of quark, which contains all local IP addresses from 172.16.23.0 to 172.16.23.255:

ip local pool quark 172.16.23.0 172.16.23.255 

Related Commands

ip address-pool
show ip local-pool

keepalive

Use the keepalive interface configuration command to set the keepalive timer for a specific interface. The no form of this command turns off keepalives entirely.

Syntax Description

Default

Enabled and set to 10 seconds on most interfaces; disabled on aysnchronous interfaces.

Command Mode

Interface configuration

Usage Guidelines

Asynchronous interfaces do not send and do not expect keepalives from the remote end of a point-to-point connection. To enable keepalives on anynchronous interfaces, use the keepalive command and set a specific interval.

You can configure the keepalive interval, which is the frequency at which the router sends messages to itself (Ethernet and Token Ring) or to the other end (serial), to ensure a network interface is alive. The interval in previous software versions was 10 seconds; it is now adjustable in 1-second increments down to 1 second. An interface is declared down after three update intervals have passed without receiving a keepalive packet.

Setting the keepalive timer to a low value is very useful for rapidly detecting Ethernet interface failures (transceiver cable disconnecting, cable unterminated, and so on).

A typical serial line failure involves losing Carrier Detect (CD). Since this sort of failure is typically noticed within a few milliseconds, adjusting the keepalive timer for quicker routing recovery is generally not useful.

Example

The following example sets the keepalive interval to 3 seconds:

interface ethernet 0
keepalive 3

lex burned-in-address

To set the burned-in MAC address for a LAN Extender interface, use the lex burned-in-address interface configuration command. To clear the burned-in MAC address, use the no form of this command.

Syntax Description

Default

No burned-in MAC address is set

Command Mode

Interface configuration

Usage Guidelines

Use this command only on a LAN Extender interface that is not currently active (not bound to a serial interface).

Example

The following example sets the burned-in MAC address on LAN Extender interface 0:

interface serial 4
encapsulation ppp
interface lex 0
lex burned-in-address 0000.0c00.0001
ip address 131.108.172.21 255.255.255.0

lex input-address-list

To assign an access list that filters on MAC addresses, use the lex input-address-list interface configuration command. To remove an access list from the interface, use the no form of this command.

Syntax Description

Default

No access lists are preassigned to a LAN Extender interface.

Command Mode

Interface configuration

Usage Guidelines

Use the lex input-address-list command to filter the packets that are allowed to pass from the LAN Extender to the core router. The access list filters packets based on the source MAC address.

The LAN Extender interface does not process MAC-address masks. Therefore, you should omit the mask from the access-list commands.

For LAN Extender interfaces, an implicit permit everything entry is automatically defined at the end of an access list. Note that this behavior differs from other router access lists, which have an implicit deny everything entry at the end of each access list.

Example

The following example applies access list 710 to LAN Extender interface 0. This access list denies all packets from MAC address 0800.0214.2776 and permits all other packets.

access-list 710 deny 0800.0214.2776 
interface lex 0
lex input-address-list 710

Related Command

A dagger (⁺) indicates that the command is documented in another chapter.

access-list ⁺

lex input-type-list

To assign an access list that filters Ethernet packets by type code, use the lex input-type-list interface configuration command. To remove an access list from the interface, use the no form of this command.

Syntax Description

Default

No access lists are preassigned to a LAN Extender interface.

Command Mode

Interface configuration

Usage Guidelines

Filtering is done on the LAN Extender chassis.

The LAN Extender interface does not process masks. Therefore, you should omit the mask from the access-list commands.

For LAN Extender interfaces, an implicit permit everything entry is automatically defined at the end of an access list. Note that this behavior differs from other router access lists, which have an implicit deny everything entry at the end of each access list.

Example

The following example applies access list 220 to LAN Extender interface 0. This access list denies all AppleTalk packets (packets with a type field of 0x809B) and permits all other packets.

access-list 220 deny 0x809B 0x0000
interface lex 0
lex input-type-list 220

Related Command

A dagger (⁺) indicates that the command is documented in another chapter.

access-list ⁺

lex priority-group

To activate priority output queuing on the LAN Extender, use the lex priority-group interface configuration command. To disable priority output queuing, use the no form of this command.

Syntax Description

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

To define queuing priorities, use the priority-list protocol global configuration command. Note that you can use only the following forms of this command:

If you specify a protocol that does not have an assigned Ethernet type code, such as x25, stun, or pad, it is ignored and will not participate in priority output queuing.

Example

The following example activates priority output queuing on LAN Extender interface 0:

priority-list 5 protocol bridge medium list 701
lex interface 0
lex priority-group 5

Related Command

A dagger (⁺) indicates that the command is documented in another chapter.

priority-list protocol ⁺

lex retry-count

To define the number of times to resend commands to the LAN Extender chassis, use the lex retry-count interface configuration command. To return to the default value, use the no form of this command.

Syntax Description

Default

10

Command Mode

Interface configuration

Usage Guidelines

After the core router has sent a command the specified number of times without receiving an acknowledgment from the LAN Extender, it stops sending the command altogether.

Example

The following example resends commands 20 times to the LAN Extender:

lex interface 0
lex retry-count 20

Related Command

lex timeout

lex timeout

To define the amount of time to wait for a response from the LAN Extender, use the lex timeout interface configuration command. To return to the default time, use the no form of this command.

Syntax Description

Default

2000 milliseconds (2 seconds)

Command Mode

Interface configuration

Usage Guidelines

The lex timeout command defines the amount of time that the core router will wait to receive an acknowledgment after having sent a command to the LAN Extender.

Example

The following example causes unacknowledged packets to be resent at 4-second intervals:

lex interface 0
lex timeout 4000

Related Command

lex retry-count

linecode

Use the linecode controller configuration command to select the line-code type for the T1 or E1 line.

Syntax Description

Defaults

AMI is the default for T1 lines.

High-density bipolar 3 is the default for E1 lines.

Command Mode

Controller configuration

Usage Guidelines

Use this command in configurations where the router is intended to communicate with T1 fractional data line. The T1 service provider determines which line-code type, either ami or b8zs, is required for your T1 circuit. Likewise, the E1 service provider determines which line-code type, either ami or hdb3, is required for your E1 circuit

Example

The following example specifies B8ZS as the line-code type:

linecode b8zs

link-test

To re-enable the link-test function on a port on an Ethernet hub of a Cisco 2505 or Cisco 2507, use the link-test hub configuration command. Disable this feature if a pre-10BaseT twisted-pair device not implementing link test is connected to the hub port with the no form of this command.

Syntax Description

This command has no arguments or keywords.

Default

Enabled

Command Mode

Hub configuration

Usage Guidelines

This command applies to a port on an Ethernet hub only. Disable this feature if a 10BaseT twisted-pair device at the other end of the hub does not implement the link test function.

Example

The following example disables the link test function on hub 0, ports 1 through 3:

hub ethernet 0 1 3
no link-test

Related Command

hub

local-lnm

To enable Lanoptics Hub Networking Management of a PCbus Token Ring interface, use the local-lnm interface configuration command. Use the no form of this command to disable Lanoptics Hub Networking Management.

Syntax Description

This command has no arguments or keywords.

Default

Management is not enabled.

Command Mode

Interface configuration

Usage Guidelines

The Token Ring interface on the AccessPro PC card can be managed by a remote LAN manager over the PCbus interface. At present, the Lanoptics Hub Networking Management software running on an IBM compatible PC is supported.

Example

The following example enables Lanoptics Hub Networking Management:

local-lnm

loopback (controller)

To loop an entire E1 line (including all channel-groups defined on the controller) toward the line and back toward the router, use the loopback controller configuration command. To remove the loop, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Controller configuration

Usage Guidelines

This command is useful for testing the DCE device (CSU/DSU) itself.

To show interfaces currently in loopback operation, use the show interfaces loopback EXEC command.

Example

The following example configures the loopback test on the E1 line:

controller e1 0
loopback 

loopback (interface)

To diagnose equipment malfunctions between interface and device, use the loopback interface configuration command. The no loopback command disables the test.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

On HSSI serial interface cards, the loopback function configures a two-way internal and external loop on the HSA applique of the specific interface.

On MCI and SCI serial interface cards, the loopback functions when a CSU/DSU or equivalent device is attached to the router. The loopback command loops the packets through the CSU/DSU to configure a CSU loop, when the device supports this feature.

On the MCI and MEC Ethernet cards, the interface receives back every packet it sends when the loopback command is enabled. Loopback operation has the additional effect of disconnecting network server functionality from the network.

On the CSC-FCI FDDI card, the interface receives back every packet it sends when the loopback command is enabled. Loopback operation has the additional effect of disconnecting network server functionality from the network.

On all Token Ring interface cards (except the 4-megabit CSC-R card), the interface receives back every packet it sends when the loopback command is enabled. Loopback operation has the additional effect of disconnecting network server functionality from the network.

Example

The following example configures the loopback test on Ethernet interface 4:

interface ethernet 4
loopback

Related Commands

down-when-looped
show interfaces loopback

loopback applique

To configure an internal loop on the HSSI applique, use the loopback interface configuration command. To remove the loop, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

This command loops the packets within the applique, thus providing a way to test for communication within the router. It is useful for sending pings to yourself to check functionality of the applique.

To show interfaces currently in loopback operation, use the show interfaces loopback EXEC command.

Example

The following example configures the loopback test on the HSSI applique:

interface serial 1
loopback applique

Related Command

show interfaces loopback

loopback dte

To loop packets back to DTE from within the local CSU/DSU, use the loopback interface configuration command. Use the no form of this command to disable the loopback.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

This command is useful for testing the DTE-to-DCE cable.

For the Cisco 2425 and Cisco 2525 router, this command is used to test the performance of the integrated CSU/DSU. Packets are looped from within the CSU/DSU back to the serial interface of the router. Send a test ping to see if the packets successfully looped back. To cancel the loopback test, use the no loopback dte command.

When using the 4-wire 56/64-kbps CSU/DSU module, an out-of-service signal is transmitted to the remote CSU/DSU.

To show interfaces currently in loopback operation, use the show interfaces loopback EXEC command.

Examples

The following example loops a packet from a module to the serial interface:

Router1(config-if)#loopback dte
Loopback in progress
Router1#ping 12.0.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/12/28 ms

Related Commands

A dagger (⁺) indicates that the command is documented in another chapter.

loopback line
loopback remote (interface)
ping ⁺
show interfaces loopback
show service-module

loopback line

To loop data received from the line at the local CSU/DSU back to the line, use the loopback line interface configuration command. The payload option determines how much of the local CSU/DSU data passes through before it is looped back to the line. Use the no form of this command to remove the loop.

Syntax Description

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

Packets are looped from an incoming network transmission back into the network at a CSU or DSU loopback point.

When the loopback line command is configured on the 2-wire 56-kbps CSU/DSU module or the 4-wire 56/64-kbps CSU/DSU modules installed on a Cisco 2524 or Cisco 2525 router, the network data loops back at the CSU and the router data loops back at the DSU. If the CSU/DSU is configured for switched mode, you must have an established connection to perform a payload-line loopback. To loop the received data through the minimum amount of CSU/DSU circuitry, issue the loopback line command.

When you issue the loopback line payload command on an integrated CSU/DSU module, the router cannot transmit data through the serial interface for the duration of the loopback. Choosing the DSU as a loopback point loops the received-network data through the maximum amount of CSU/DSU circuitry. Data is not looped back to the serial interface. An active connection is required when operating in switched mode for payload loopbacks.

If you enable the loopback line command on the fractional T1/T1 module, the CSU/DSU performs a full-bandwidth loopback through the CSU portion of the module and data transmission through the serial interface is interrupted for the duration of the loopback. No reframing or corrections of bi polar violation errors or cyclic redundancy checksum (CRC) errors are performed. When you configure the line loopback payload command on the FT1/T1 module, the CSU/DSU performs a loopback through the DSU portion of the module. The line loopback payload command reframes the data link, regenerates the signal, and corrects bi polar violations and extended super frame CRC errors.

When performing a T1-line loopback with extended super framing, communication over the facilities data link is interrupted, but performance statistics are still updated. To show interfaces currently in loopback operation, use the show service-module EXEC command.

Examples

The following example shows how to configure a payload loopback:

Router1(config-if)#loopback line payload
Loopback in progress
Router1(config-if)#no loopback line

The following example shows the output when you loop a packet in switched mode without an active connection:

Router1(config-if)#service-module 56k network-type switched
Router1(config-if)#loopback line payload
Need active connection for this type of loopback
% Service module configuration command failed: WRONG FORMAT.

The following example configures the loopback test on the DCE device:

interface serial 1
loopback line

Related Command

show interfaces loopback

loopback local (controller)

To loop an entire T1 line (including all channel-groups defined on the controller) toward the line and back toward the router, use the loopback local controller configuration command. To remove the loop, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Controller configuration

Usage Guidelines

This command is useful for testing the DCE device (CSU/DSU) itself.

To show interfaces currently in loopback operation, use the show interfaces loopback EXEC command.

Example

The following example configures the loopback test on the T1 line:

controller t1 0
loopback local

loopback local (interface)

To loop a channelized T1 or channelized E1 channel-group, use the loopback local interface configuration command. To remove the loop, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

This command is useful for looping a single channel-group in a channelized environment without disrupting the other channel-groups.

To show interfaces currently in loopback operation, use the show interfaces loopback EXEC command.

Example

The following example configures the loopback test on the T1 line:

interface serial 1/0:22
loopback local

Related Command

show interfaces loopback

loopback remote (controller)

To loop packets from a MIP through the CSU/DSU, over a dedicated T1 link, to the remote CSU at the single destination for this T1 link and back, use the loopback remote controller configuration command. To remove the loop, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Controller configuration

Usage Guidelines

This command applies only when the device supports the remote function. It is used for testing the data communication channels.

For MIP cards, this controller configuration command applies if only one destination exists at the remote end of the cloud, the entire T1 line is dedicated to it, and the device at the remote end is a CSU (not a CSU/DSU). This is an uncommon case; MIPs are not usually used in this way.

To show interfaces currently in loopback operation, use the show interfaces loopback EXEC command.

Example

The following example configures a remote loopback test:

interface serial 0
loopback remote

Related Command

show interfaces loopback

loopback remote (interface)

To loop packets through a CSU/DSU, over a DS-3 link or a channelized T1 link, to the remote CSU/DSU and back, use the loopback remote interface configuration command. To remove the loopback, use the no form of this command.

Syntax Description for the FT1/T1 CSU/DSU Module

Syntax Description for the 2- and 4-Wire 56/64-kbps CSU/DSU Modules

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

This command applies only when the remote CSU/DSU device is configured for this function. It is used for testing the data communication channels along with or without remote CSU/DSU circuitry. The loopback is usually performed at the line port, rather than the DTE port, of the remote CSU/DSU.

For a multiport interface processor connected to a network via a channelized T1 link, the loopback remote interface configuration command applies if the remote interface is served by a DDS line (56 kbps or 64 kbps) and the device at the remote end is a CSU/DSU. In addition, the CSU/DSU at the remote end must react to latched DDS CSU loopback codes. Destinations that are served by other types of lines or that have CSU/DSUs that do not react to latched DDS CSU codes cannot participate in an interface remote loopback. Latched DDS CSU loopback code requirements are described in AT&T specification TR-TSY-000476, "OTGR Network Maintenance Access and Testing."

On the integrated FT1/T1 CSU/DSU module installed on a Cisco 2524 and Cisco 2525 router, the loopback remote full command sends the loopup code to the remote CSU/DSU. The remote CSU/DSU performs a full-bandwidth loopback through the CSU portion of the module. The loopback remote payload command sends the loopup code on the configured timeslots, while maintaining the D4-extended super framing. The remote CSU/DSU performs the equivalent of a loopback line payload request. The remote CSU/DSU loops back only those timeslots that are configured of the remote end. This loopback reframes the data link, regenerates the signal, and corrects bi polar violations and extended super frame CRC errors. The loopback remote smart-jack command sends a loopup code to the remote smart jack. You cannot put the local smart jack into loopback.

Failure to loopup or initiate a remote loopback request could be caused by enabling the no service-module t1 remote-loopback command or having an alternate remote-loopback code configured on the remote end. When the loopback is terminated, the result of the pattern test is displayed.

On the 2- and 4-wire 56/64-kbps CSU/DSU modules installed on a Cisco 2524 or Cisco 2525 router, an active connection is required before a loopup can be initiated while in switched mode. When transmitting V.54 loopbacks, the remote device is commanded into loopback using V.54 messages. Failure to loopup or initiate a remote loopback request could be caused by enabling the no service-module 56k remote-loopback command.

To show interfaces currently in loopback operation, use the show interfaces loopback EXEC command.

Examples

The following example configures a remote loopback test:

Router(config)#interface serial 0
Router(config)#loopback remote

The following example configures the remote device into full-bandwidth line loopback while specifying the qrw test pattern over the T1 CSU/DSU module on a Cisco 2524 or Cisco 2525 router:

Router(config)#interface serial 0
Router(config-if)#loopback remote full qrw
Router(config-if)#
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to down
%LINK-3-UPDOWN: Interface Serial0, changed state to down
%SERVICE_MODULE-5-LOOPUPREMOTE: Unit 0 - Remote unit placed in loopback

The following example transmits a remote loopback stress pattern over the 4-wire 56/64-kbps CSU/DSU module, which tests the stress clocking of the network:

Router(config-if)#loopback remote stress-pattern 1
Router(config-if)#
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1, changed state to down
%LINK-3-UPDOWN: Interface Serial1, changed state to down
%SERVICE_MODULE-5-LOOPUPREMOTE: Unit 1 - Remote unit placed in loopback

Related commands

clear service-module
loopback dte
loopback line
service-module t1 remote-loopback
service-module 56k remote-loopback
show interfaces loopback
show service-module

media-type

Use the media type command to specify one of the following configurations:

• to specify the Ethernet Network Interface Module configuration on the Cisco 4000 series

• to specify the FEIP on the Cisco 7000 series

Use the no form of this command to restore the default value.

Syntax Description

Defaults

AUI 15-pin physical connection is the default setting on the Cisco 4000 series.

100BaseT physical connection is the default setting on the Cisco 7000 series.

Command Mode

Interface configuration

Examples

The following example specifies an RJ45 10BaseT physical connection to Ethernet interface 1:

interface ethernet 1
media-type 10baset

The following example specifies a media-independent interface physical connection to Fast Ethernet slot 0, port 1 on the Cisco 7000:

interface fastethernet 0/1
media-type mii

member

To alter the configuration of an asynchronous interface that is a member of a group, use the member interface configuration command. Use the no form of the command to restore defaults set at the group master interface.

Syntax Description

Default

No individual configurations are set for member interfaces.

Command Mode

Interface configuration

Usage Guidelines

You can customize a member interface by using the member command. (Interfaces are designated as members of a group by using the interface group-async and group-range commands). To restore the defaults set at the group master interface, use the no form of this command.

Examples

The following example defines interface 3 as having a description of line 3, attached to a Hayes Optima modem:

interface group-async 0
member 3 description line #3 Hayes Optima

Related Commands

group-range
interface group-async

mop enabled

To enable an interface to support the Maintenance Operation Protocol (MOP), use the mop enabled interface configuration command. To disable MOP on an interface, use the no mop enabled command.

Syntax Description

This command has no arguments or keywords.

Default

Enabled on Ethernet interfaces and disabled on all other interfaces.

Command Mode

Interface configuration

Example

In the following example, MOP is enabled for serial interface 0:

interface serial 0
mop enabled

Related Commands

A dagger (⁺) indicates that the command is documented in another chapter.

mop sysid
mop retransmit-timer ⁺
mop retries ⁺

mop sysid

To enable an interface to send out periodic Maintenance Operation Protocol (MOP) system identification messages, use the mop sysid interface configuration command. To disable MOP message support on an interface, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Default

Enabled

Command Mode

Interface configuration

Usage Guidelines

You can still run MOP without having the background system ID messages sent. This lets you use the MOP remote console, but does not generate messages used by the configurator.

Example

In the following example, serial interface 0 is enabled to send MOP system identification messages:

interface serial 0
mop sysid

Related Commands

A dagger (⁺) indicates that the command is documented in another chapter.

mop device-code ⁺
mop enabled

mtu

To adjust the maximum packet size or maximum transmission unit (MTU) size, use the mtu interface configuration command. Use the no form of this command to restore the MTU value to its original default value.

Syntax Description

Defaults

Table 6-9 lists default MTU values according to media type.

Command Mode

Interface configuration

Usage Guidelines

Each interface has a default maximum packet size or maximum transmission unit (MTU) size. This number generally defaults to the largest size possible for that type interface. On serial interfaces, the MTU size varies, but cannot be set smaller than 64 bytes.

Example

The following example specifies an MTU of 1000 bytes:

interface serial 1
mtu 1000

Related Commands

A dagger (⁺) indicates that the command is documented in another chapter.

encapsulation smds ⁺
ip mtu ⁺

nrzi-encoding

To enable non-return to zero inverted (NRZI) line coding format, use the nrzi-encoding interface configuration command. Use the no form of this command to disable this capability.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

All FSIP interface types support nonreturn to zero (NRZ) and nonreturn to zero inverted (NRZI) format. This is a line coding format that is required for serial connections in some environments. NRZ encoding is most common. NRZI encoding is used primarily with RS-232 connections in IBM environments.

Example

In the following example, serial interface 1 is configured for NRZI encoding:

interface serial 1
nrzi-encoding

peer default ip address

Use the peer default ip address command to specify an IP address, an address from a specific IP address pool, or an address from the DHCP mechanism to be returned to a remote peer connecting to this interface. Use the no form of the command to disable a prior peer IP address pooling configuration on an interface.

Syntax Description

Default

pool

Command Mode

Interface configuration

Usage Guidelines

This command applies to point-to-point interfaces that support the PPP or SLIP encapsulation.

This command allows an administrator to configure all possible address pooling mechanisms on a interface-by-interface basis.

The peer default ip address command can be used to override on an interface-by-interface basis the Global Default Mechanism defined by the ip address-pool command.

• For all interfaces not configured with a peer default IP address mechanism (equivalent to selecting the peer default ip address pool command), the router uses the Global Default Mechanism that is defined by the ip address-pool command.

• If you select the peer default ip address pool poolname command, then the router uses the locally configured pool on this interface and does not follow the Global Default Mechanism.

• If you select the peer default ip address ip-address form of this command, the specific IP address is assigned to any peer connecting to this interface and any Global Default Mechanism is overridden for this interface.

• If you select the peer default ip address dhcp form of this command, the DHCP proxy-client mechanism is used by default on this interface and any Global Default Mechanism is overridden for this interface.

Examples

The following command specifies that this interface will use a local IP address pool called shazam:

peer default ip address pool shazam

The following command specifies that this interface will use the IP address 172.140.34.21:

peer default ip address 172.140.34.21

The following command reenables the Global Default Mechanism to be used on this interface:

peer default ip address pool

Related Commands

A dagger (⁺) indicates that the command is documented in another chapter.

encapsulation ppp
encapsulation slip
ip address-pool
ip dhcp-server
ip local pool
ppp ⁺
slip⁺
show dhcp

peer neighbor-route

To reenable the creation of peer neighbor routes on an interface once this default behavior has been disabled, use the peer neighbor-route interface configuration command. To disable the default behavior of creating a neighbor route for the peer on a point-to-point interface, use the no form of this command.

Syntax Description

This command has no keywords and arguments.

Default

Creation of a route to the peer address on any point-to-point interface when the PPP IPCP negotiation is completed.

Command Mode

Interface configuration

Usage Guidelines

Use the no form of this command only if the default behavior creates problems in your network environment.

If if you enter this command on a dialer interface or a async-group interface, it affects all member interfaces.

Example

The following examples reenables the default behavior on an interface.

peer neighbor-route 

physical-layer

To specify the mode of a slow-speed serial interface on a router as either synchronous or asynchronous, use the physical-layer interface configuration command. Use the no form of this command to return the interface to its default mode, which is synchronous.

Syntax Description

Default

Synchronous mode.

Command Mode

Interface Configuration

Usage Guidelines

This command applies only to low-speed serial interfaces available on Cisco 2520 through 2523 routers.

If you specify the no physical-layer command, you return the interface to its default mode (synchronous).

In synchronous mode, low-speed serial interfaces support all interface configuration commands available for high-speed serial interfaces, except the following two commands:

• sdlc cts-delay

• sdlc rts-timeout

When placed in asynchronous mode, low-speed serial interfaces support all commands available for standard asynchronous interfaces.

When you enter this command, it does not appear in the output of show running config and show startup config commands, because the command is a physical layer command.

Examples

The following examples show different uses of this command.

The following example shows how to change a low-speed serial interface from synchronous to asynchronous mode:

Cobra(config)# interface serial 2
Cobra(config-if)# physical-layer async

The following examples show how to change a low-speed serial interface from asynchronous mode back to its default synchronous mode:

Cobra(config)# interface serial 2
Cobra(config-if)# physical-layer sync

or

Cobra(config)# interface serial 2
Cobra(config-if)# no physical-layer

The following example shows some typical asynchronous interface configuration commands:

Cobra(config)# interface serial 2
Cobra(config-if)# physical-layer async
Cobra(config-if)# ip address 1.0.0.2 255.0.0.0 
Cobra(config-if)# async default ip address 1.0.0.1
Cobra(config-if)# async mode dedicated
Cobra(config-if)# async default routing

The following example shows some typical synchronous serial interface configuration commands available when the interface is in synchronous mode:

Cobra(config)# interface serial 2
Cobra(config-if)# physical-layer sync
Cobra(config-if)# ip address 1.0.0.2 255.0.0.0 
Cobra(config-if)# no keepalive
Cobra(config-if)# ignore-dcd
Cobra(config-if)# nrzi-encoding
Cobra(config-if)# no shutdown

Related Commands

half-duplex controlled-carrier
half-duplex timer

ppp authentication

To enable Challenge Handshake Authentication Protocol (CHAP) or Password Authentication Protocol (PAP), and to enable a TACACS+ authorization method on a serial interface, use the ppp authentication interface configuration command. Use the no form of the command to disable this authentication.

Syntax Description

Default

PPP authentication is not enabled.

Command Mode

Interface configuration

Usage Guidelines

Once you have enabled CHAP or PAP, the local communication server requires a password from remote devices. If the remote device does not support CHAP or PAP, no traffic is passed to that device.

If you are using autoselect on a TTY line, you will probably want to use the ppp authentication command to turn on PPP authentication for the corresponding interface.

When you specify the if-needed option, PPP authentication is not required when the user has already provided authentication. This option is useful in conjunction with the autoselect command, but cannot be used with AAA/TACACS+.

The list-name keyword can be used only when AAA/TACACS+ has been initialized, and cannot be used with the if-needed argument.

Example

The following example enables CHAP on asynchronous interface 4, and uses the authentication list MIS-access:

interface async 4
encapsulation ppp
ppp authentication chap MIS-access

Related Commands

autoselect
dialer map
encapsulation ppp
ppp use-tacacs
username password
aaa authentication ppp
aaa new-model

ppp chap password

To configure a common CHAP secret to be used in responses to challenges from an unknown remote peer in a collection of routers that do not support this command (such as routers running older Cisco IOS software images), use the ppp chap password interface configuration command. To disable this function, use the no form of this command.

Syntax Description

Default

Disabled.

Command Mode

Interface configuration

Usage Guidelines

This command allows you to replace several username and password configuration commands with a single copy of this command on any dialer interface or asynchronous group interface.

This command is used for remote CHAP authentication only (when authenticating to the peer) and does not affect local CHAP authentication.

Example

The following example configures interface BRI 0 for PPP encapsulation. If a CHAP challenge is received from a peer whose name is not found in the global list of usernames, the encrypted secret 7 1267234591 is decrypted and used to create a CHAP response value.

interface bri0
encapsulation ppp
ppp chap password 7 1234567891 

Related Commands

A dagger (⁺) indicates that the command is documented outside this chapter.

ppp authentication
aaa authentication ppp ⁺
ppp pap ⁺
ppp chap hostname ⁺

ppp compress

To configure software compression for Point-to-Point Protocol (PPP) encapsulation, use the ppp compress interface configuration command. To disable compression, use the no form of this command.

Syntax Description

Default

PPP compression is disabled.

Command Mode

Interface configuration

Usage Guidelines

Compression reduces the size of frames via lossless data compression. The compression algorithm used is a predictor algorithm (the RAND compression algorithm), which uses a compression dictionary to predict what the next character in the frame will be.

Examples

The following example enables predictor compression on serial interface 0:

interface serial 0
encapsulation ppp
ppp compress predictor

Related Commands

encapsulation ppp
show compress

ppp quality

To enable Link Quality Monitoring (LQM) on a serial interface, use the ppp quality interface configuration command. Use the no form of this command to disable LQM.

Syntax Description

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

The percentages are calculated for both incoming and outgoing directions. The outgoing quality is calculated by comparing the total number of packets and bytes sent to the total number of packets and bytes received by the peer. The incoming quality is calculated by comparing the total number of packets and bytes received to the total number of packets and bytes sent by the peer.

If the link quality percentage is not maintained, the link is deemed to be of poor quality and is taken down. The policy implements a time lag so that the link does not bounce up and down.

Example

The following example enables LQM on serial interface 4:

interface serial 4
encapsulation ppp
ppp quality 80

Related Commands

encapsulation ppp
keepalive

ppp reliable-link

To enable LAPB Numbered Mode negotiation for a reliable serial link, use the ppp reliable-link interface configuration command. To disable negotiation for a PPP reliable link on a specified interface, use the no form of the command.

Syntax Description

This command has no arguments and keywords.

Default

Disabled

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.0.

Enabling LAPB Numbered Mode negotiation as a means of providing a reliable link does not guarantee that all connections through the specified interface will in fact use reliable link. It only guarantees that the router will attempt to negotiate reliable link on this interface.

PPP reliable link can be used with PPP compression over the link, but it does not require PPP compression.

You can use the show interface command to determine whether LAPB has been established on the link. You can troubleshoot PPP reliable link by using the debug lapb command and the debug ppp negotiations, debug ppp errors, and debug ppp packets commands.

Example

The following example enables PPP reliable link and predictor compression on interface serial 1:

interface serial 1
 description Enables predictor compression on Serial 1
 ip address 170.1.1.1 255.255.255.0 
 encapsulation ppp
 dialer map ip 170.1.1.2 name starbuck 14195291357
 compress predictor
 ppp authentication chap
 dialer-group 1
 ppp reliable-link

Related Commands

debug lapb
debug ppp
compress
show interface

pri-group

To specify ISDN Primary Rate Interface (PRI) on a channelized E1 or T1 card on the Cisco 7000 series, use the pri-group controller configuration command. Use the no form of this command to remove the ISDN PRI.

Syntax Description

Default

Disabled

Command Mode

Controller configuration

Usage Guidelines

When you configure ISDN PRI, you must first specify an ISDN switch type for PRI and an E1 or T1 controller.

Example

The following example specifies ISDN PRI on T1 slot 1, port 0:

isdn switch-type primary-4ess
controllers t1 1/0
framing esf
linecode b8zs
pri-group timeslots 2-6

Related Commands

controller
framing
isdn switch-type
linecode

pulse-time

To enable pulsing DTR signal intervals on the serial interfaces, use the pulse-time interface configuration command. Use the no form of this command to restore the default interval.

Syntax Description

Default

0 seconds

Command Mode

Interface configuration

Usage Guidelines

When the serial line protocol goes down (for example, because of loss of synchronization) the interface hardware is reset and the DTR signal is held inactive for at least the specified interval. This function is useful for handling encrypting or other similar devices that use the toggling of the DTR signal to resynchronize.

Example

The following example enables DTR pulse signals for three seconds on serial interface 2:

interface serial 2
pulse-time 3

ring-speed

To set the ring speed for the CSC-1R and CSC-2R Token Ring interfaces, use the ring-speed interface configuration command.

Syntax Description

Default

16-Mbps operation

Command Mode

Interface configuration

Example

The following example sets a Token Ring interface ring speed to 4 Mbps:

interface tokenring 0
ring-speed 4

service-module t1 clock source

To specify the clock source for the fractional T1/T1 CSU/DSU module installed in a Cisco 2524 or Cisco 2525 router, use the service-module t1 clock source interface configuration command. Use the no form of this command to enable the line clock.

Syntax Description

Default

Line clock

Command Mode

Interface configuration

Example

The following example sets an internal clock source on serial line 0:

Router(config-if)#interface serial 0

Router(config-if)#service-module t1 clock source line

Related Commands

service-module 56k clock source

service-module t1 data-coding

To guarantee the ones density requirement on an AMI line using the fractional T1/T1 module, use the service-module t1 data-coding interface configuration command. Use the no form of this command to enable normal data transmission.

Syntax Description

Default

Normal transmission

Command Mode

Interface configuration

Usage Guidelines

This command applies to the Cisco 2524 and Cisco 2525 routers.

Data inversion is used to guarantee the ones density requirement on an AMI line when using bit-oriented protocols such as High-Level Data Link Control (HDLC), Point-to-Point Protocol (PPP), X.25, and Frame Relay. If the timeslot speed is set to 56 kbps, this command is rejected because line density is guaranteed when transmitting at 56 kbps. Use this command with the 64-kbps line speed.

If you transmit inverted bit codes, both CSU/DSUs must have this command configured for successful communication.

Example

The following example shows how to invert bit codes using a timeslot speed of 64 kbps:

Router(config-if)#service-module t1 timeslots all speed 56
Router(config-if)#service-module t1 data-coding inverted
Cannot choose inverted data mode if timeslot speed is 56kbps
% Service module configuration command failed: WRONG FORMAT.
Router(config-if)#service-module t1 timeslots all speed 64
Router(config-if)#service-module t1 data-coding inverted

Related Commands

service-module t1 linecode
service-module t1 timeslots

service-module t1 framing

To select the frame type for a line using the fractional T1/T1 (FT1/T1) module from a Cisco 2524 or Cisco 2525 router, use the service-module t1 framing interface configuration command. Use the no form of this command to select the default, which is extended-super frame as the T1 frame type.

Syntax Description

Default

esf

Usage Guidelines

Use this command in configurations where the router communicates with FT1/T1 data lines. The service provider determines which framing type, either esf or sf, is required for your circuit.

Example

The following example enables super frame as the FT1/T1 frame type:

Router1(config-if)#service-module t1 framing sf

service-module t1 lbo

To configure the CSU line build out on a fractional T1/T1 CSU/DSU module, use the service-module lbo interface configuration command. Use the no form of this command to disable line build out.

Syntax Description

Default

No line build out

Usage Guidelines

This command applies to the Cisco 2524 and Cisco 2525 routers.

Use this command to decrease the outgoing signal strength to an optimum value for a fractional T1 line receiver. The ideal signal strength should be between -15 dB and -22 dB, which is calculated by adding the phone company loss + cable length loss + line build out.

Example

The following example shows a lbo setting of -7.5 dB:

Router1(config-if)#service-module t1 lbo -7.5db

service-module t1 linecode

To select the line-code type for the fractional T1/T1 module installed on a Cisco 2524 or Cisco 2525 router, use the service-module t1 linecode interface configuration command. Use the no form of this command to select the default, which is the B8ZS line code.

Syntax Description

Default

Line code is b8zs

Command Mode

Interface configuration

Usage Guidelines

Configuring B8ZS is a method of ensuring the ones density requirement on a T1 line by substituting intentional bi polar violations in bit positions four and seven for a sequence of eight zero bits. When the CSU/DSU is configured for AMI, you must guarantee the ones density requirement in your router configuration using the service-module t1 data-coding inverted command or the service-module t1 timeslots speed 56 command.

Your T1 service provider determines which line-code type, either ami or b8zs, is required for your T1 circuit.

Example

The following example specifies AMI as the line-code type:

Router1(config-if)# service-module t1 linecode ami

Related Commands

service-module t1 data-coding
service-module t1 timeslots

service-module t1 remote-alarm-enable

To generate remote alarms (yellow alarms) at the local CSU/DSU or detect remote alarms sent from the remote CSU/DSU, use the service-module t1 remote-alarm-enable interface configuration command. Use the no form of this command to disable remote alarms.

Syntax Description

This command has no arguments or keywords.

Default

Remote alarms disabled

Command Mode

Interface configuration

Usage Guidelines

This command applies to the fractional T1/T1 CSU/DSU module installed on Cisco 2524 and Cisco 2525 routers.

Remote alarms are transmitted by the CSU/DSU when it detects an alarm condition, such as a red alarm (loss of frame) or blue alarm (unframed 1s). The receiving CSU/DSU then knows there is an error condition on the line.

With D4 super frame configured, a remote alarm condition is transmitted by setting the bit 2 of each time slot to zero. For received user data that has the bit 2 of each time slot set to zero, the CSU/DSU interprets the data as a remote alarm and interrupts data transmission, which explains why remote alarms are disabled by default. With extended super frame configured, the remote alarm condition is signalled out of band in the facility data link.

You can see if the FT1/T1 CSU/DSU is receiving a remote alarm (yellow alarm) by issuing the show service-module command.

Related Commands

service-module t1 framing

service-module t1 remote-loopback

To specify if the fractional T1/T1 CSU/DSU module enters loopback mode when it receives a loopback code on the line, use the service-module t1 remote-loopback interface configuration command. Use the no form of this command to disable remote loopbacks.

Syntax Description

Default

Full and payload loopbacks with standard-loopup codes.

Command Mode

Interface configuration

Usage Guidelines

This command applies only to the Cisco 2524 and Cisco 2525 routers

You can simultaneously configure the full and payload loopback points. However, only one loopback code can be configured at a time. For example, if you configure the service-module t1 remote-loopback payload alternate command, a payload v54 request cannot be transmitted or accepted.

The no form of this command disables loopback requests. For example, the no service-module t1 remote-loopback full command ignores all full-bandwidth loopback transmissions and requests. Configuring the no form of the command may not prevent telco line providers from looping your router in esf mode, because fractional T1/T1 lines use facilities data link messages to initiate loopbacks.

If you enable the service-module t1 remote-loopback command, the loopback remote commands on the FT1/T1 CSU/DSU module will not be successful.

Example

The following example displays two routers connected back-to-back through a fractional T1/T1 line:

Router3(config-if)#no service-module t1 remote-loopback full
Router3(config-if)#service-module t1 remote-loopback payload alternate

Router1(config-if)#loopback remote full
%SERVICE_MODULE-5-LOOPUPFAILED: Unit 0 - Loopup of remote unit failed

Router1(config-if)#service-module t1 remote-loopback payload v54
Router1(config-if)#loopback remote payload
%SERVICE_MODULE-5-LOOPUPFAILED: Unit 0 - Loopup of remote unit failed

Router1(config-if)#service-module t1 remote-loopback payload alternate
Router1(config-if)#loopback remote payload
%SERVICE_MODULE-5-LOOPUPREMOTE: Unit 0 - Remote unit placed in loopback

Related Commands

loopback remote (interface)

service-module t1 timeslots

To define timeslots for the fractional T1/T1 (FT1/T1) module installed in a Cisco 2524 or Cisco 2525 router, use the service-module t1 timeslots interface configuration command. Use the no form of this command to select all FT1/T1 timeslots transmitting at 64 kbps.

Syntax Description

Default

All timeslots selected and transmitting at 64 kbps.

Command Mode

Interface configuration

Usage Guidelines

The timeslot range must match the timeslots assigned to the channel group. Your service provider defines the timeslots that comprise a channel group.

Examples

The following example displays a series of timeslot ranges and a speed of 64 kbps:

Router(config-if)#service-module t1 timeslots 1-10,15-20,22 speed 64

Related commands

service-module t1 linecode

service-module 56k clock rate

To configure the network line speed for a 4-wire 56/64-kbps CSU/DSU module, use the service-module 56k clock rate interface configuration command. Use the no form of this command to enable a network line speed of 56 kbps.

Syntax Description

Default

56 kbps

Command Mode

Interface configuration

Usage Guidelines

Configure the line with the following speeds: 2.4, 4.8, 9.6, 19.2, 38.4, 56, and 64. The 64-kbps line speed cannot be used with back-to-back digital data service (DDS) lines. The sub rate line speeds are determined by the service provider.

Only the 56-kbps line speed is available in switched mode, which is enabled using the service-module 56k network-type interface configuration command on the 4-wire CSU/DSU. The 2-wire CSU/DSU default is set to switched mode.

The keyword auto enables the CSU/DSU to decipher current line speed from the sealing current running on the network. Use auto only when transmitting over telco DDS lines and the clocking source is taken from the line.

Example

The following example displays two routers connected in back-to-back DDS mode. However, the configuration fails because the auto rate is used.

Router1(config-if)#service-module 56k clock source internal
Router1(config-if)#service-module 56k clock rate 38.4
Router2(config-if)#service-module 56k clock rate auto
% WARNING - auto rate will not work in back-to-back DDS.
a1#ping 10.1.1.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.2, timeout is 2 seconds:
.....		
Success rate is 0 percent (0/5)
Router2(config-if)#service-module 56k clock rate 38.4 
Router1#ping 10.1.1.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 52/54/56 ms

When transferring from DDS mode to switched mode, you must set the correct clock rate, as shown in the following example:

Router2(config-if)#service-module 56k network-type dds
Router2(config-if)#service-module 56k clock rate 38.4
Router2(config-if)#service-module 56k network-type switched
% Have to use 56k or auto clock rate for switched mode
% Service module configuration command failed: WRONG FORMAT.
Router2(config-if)#service-module 56k clock rate auto
% WARNING - auto rate will not work in back-to-back DDS.
Router2(config-if)#service-module 56k network-type switched

Related Commands

service-module 56k network-type
service-module 56k clock source

service-module 56k clock source

To configure the clock source for a 4-wire 56/64-kbps CSU/DSU module, use the service-module 56k clock source interface configuration command. Use the no form of this command to enable the line clock.

Syntax Description

Default

The line clock provided by the telco service provider.

Command Mode

Interface configuration

Example

The following example shows a router using internal clocking while transmitting frames at 38.4 kbps.

Router1(config-if)#service-module 56k clock source internal
Router1(config-if)#service-module 56k clock rate 38.4

Related Commands

service-module 56k clock rate

service-module 56k data-coding

To prevent application data from replicating loopback codes when operating at 64-kbps on a 4-wire CSU/DSU, use the service-module 56k data-coding interface configuration command. Use the no form of this command to enable normal transmission.

Syntax Description

Default

Normal data transmission

Command Mode

Interface configuration

Usage Guidelines

This command applies only to the Cisco 2524 or Cisco 2525 router.

Enable the scrambled configuration only in 64-kbps digital data service (DDS) mode. If the network type is set to switched, the configuration is refused.

If you transmit scrambled bit codes, both CSU/DSUs must have this command configured for successful communication.

Example

The following example enables the service-module 56k data-coding scrambled command:

Router1(config-if)#service-module 56k clock rate 56
Router1(config-if)#service-module 56k data-coding scrambled
Can configure scrambler only in 64k speed DDS mode
% Service module configuration command failed: WRONG FORMAT.
Router1(config-if)#service-module 56k clock rate 64
Router1(config-if)#service-module 56k data-coding scrambled

Related Commands

service-module 56k clock rate

service-module 56k network-type

To transmit packets in switched dial-up mode or digital data service (DDS) mode using the 4-wire 56/64-kbps CSU/DSU module, use the service-module 56k network-type interface configuration command. Use the no form of this command to transmit from a dedicated leased line in DDS mode.

Syntax Description

Default

DDS is enabled for the 4-wire CSU/DSU

Switched is enabled for the 2-wire CSU/DSU

Command Mode

Interface configuration

Usage Guidelines

This command applies to the Cisco 2524 and Cisco 2525 routers.

Active telco lines transmit in switched mode, which requires additional dialer configuration commands to configure dial-out numbers. Before you enable the service-module 56k network-type switched command, both CSU/DSU's must use a line clocking and clock rate configured to auto or 56k kbps. If the clock rate is not set correctly, this command will not be accepted.

The 2-wire and 4-wire 56/64-kbps CSU/DSU modules accept V.25 bis dial commands, which are configured using the dialer in-band command.

Example

The following example displays transmission in switched dial-up mode:

Router(config-if)#service-module 56k clock rate 19.2
Router(config-if)#service-module 56k network-type switched
% Have to use 56k or auto clock rate for switched mode
% Service module configuration command failed: WRONG FORMAT.
Router(config-if)#service-module 56k clock rate auto
Router(config-if)#service-module 56k network-type switched
Router(config-if)#dialer in-band
Router(config-if)#dialer string 2576666
Router(config-if)#dialer-group 1

Related Commands

A dagger (⁺) indicates that the command is documented in another chapter.

dialer in-band⁺
service-module 56k clock rate
service-module 56k clock source
service-module 56k switched-carrier

service-module 56k remote-loopback

To enable the acceptance of a remote loopback request on a 2- or 4-wire 56/64-kbps CSU/DSU module, use the service-module 56k remote-loopback interface configuration command. Use the no form of this command to disable the module from entering loopback.

Syntax Description

This command has no arguments or keywords.

Default

Enabled

Command Mode

Interface configuration

Usage Guidelines

This command applies to the Cisco 2524 and Cisco 2525 routers.

The no service-module 56k remote-loopback command prevents the local CSU/DSU from being placed into loopback by remote devices on the line. The line provider is still able to put the module into loopback by reversing sealing current. Unlike the T1 module, the 2- or 4-wire 56/64-kbps CSU/DSU module can still initiate remote loopbacks with the no form of this command configured.

Examples

The following example enables you to transmit and receive remote loopbacks using the service-module 56k remote-loopback command:

Router(config-if)#service-module 56k remote-loopback
Router(config-if)#
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to down
%LINK-3-UPDOWN: Interface Serial0, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to up
%LINK-3-UPDOWN: Interface Serial0, changed state to up
%SERVICE_MODULE-5-LOOPUPREMOTE: Unit 0 - Remote unit placed in loopback

Related Commands

loopback remote (interface)

service-module 56k switched-carrier

To select a service provider to use with a 2-wire or 4-wire 56/64 kbps dial-up line, use the service-module 56k switched-carrier interface configuration command. Use the no form of this command to enable the default service provider.

Syntax Description

Default

ATT is enabled on the 4-wire 56/64-kbps CSU/DSU module.

Sprint is enabled on the 2-wire switched 56-kbps CSU/DSU module.

Command Mode

Interface configuration

Usage Guidelines

Use this command only on the 2- or 4-wire 56/64-kbps CSU/DSU modules installed on a Cisco 2524 or Cisco 2525 router.

On a Sprint network, echo-canceler tones are sent during call setup to prevent the echo cancelers from damaging digital data. The transmission of echo-canceler tones may increase call setup times by 8 seconds on the 4-wire module. Having echo cancellation enabled does not affect data traffic.

This configuration command is ignored if the network type is DDS.

Example

The following example displays choosing AT&T as a service provider:

Router(config-if)#service-module 56k network-type switched
Router(config-if)#service-module 56k switched-carrier att

Related Commands

service-module 56k network-type

show async status

To list the status of the asynchronous interface 1 associated with the router auxiliary port, use the show async status user EXEC command:

Syntax Description

This command has no arguments or keywords.

Command Mode

EXEC

Usage Guidelines

Shows all asynchronous sessions, whether they are using SLIP or PPP encapsulation.

Sample Display

The following is sample output from the show async status command:

Router> show async status
Async protocol statistics:
  Rcvd: 5448 packets, 7682760 bytes
        1 format errors, 0 checksum errors, 0 overrun, 0 no buffer
  Sent: 5455 packets, 7682676 bytes, 0 dropped
 Int           Local          Remote Qd InPack OutPac Inerr  Drops  MTU Qsz
   1     192.31.7.84         Dynamic  0      0      0     0      0 1500  10

Table 6-10 describes significant fields shown in the display.

Related Commands

async default ip address
async dynamic address
async dynamic routing
async mode dedicated
async mode interactive
interface async

show compress