|
|
Use the commands in this chapter to configure Link Access Procedure Balanced (LAPB), X.25, Defense Data Network (DDN) X.25, and Blacker Front End (BFE). X.25 provides remote terminal access; encapsulation for the IP, DECnet, XNS, ISO CLNS, AppleTalk, Novell IPX, Banyan VINES, and Apollo Domain protocols; and bridging.
X.25 virtual circuits can also be switched
To translate between X.25 and another protocol, refer to the Protocol Translation Configuration Guide and Command Reference publication.
For X.25 and LAPB configuration information and examples, refer to the "Configuring X.25 and LAPB" chapter in the Router Products Configuration Guide.
To allow the router to participate in emergency mode or to end participation in emergency mode when the interface is configured for x25 bfe-emergency decision and x25 bfe-decision ask, use the bfe EXEC command.
bfe {enter | leave} type numberEXEC
The following example enables an interface to participate in BFE emergency mode:
bfe enter serial 0
encapsulation x25
x25 bfe-decision
x25 bfe-emergency
To clear switched virtual circuits (SVCs) and to reset permanent virtual circuits (PVCs), use the clear x25-vc privileged EXEC command. To clear all X.25 virtual circuits at once by restarting the packet layer service, use this command without an lcn argument.
clear x25-vc type number [lcn]| type | Interface type. |
| number | Interface number. |
| lcn | (Optional) Virtual circuit. |
Privileged EXEC
The following example illustrates how to clear all virtual circuits on an interface:
clear x25-vc serial 1
To enable Connection-Mode Network Service (CMNS) on a nonserial interface, use the cmns enable interface configuration command. To disable this capability, use the no form of this command.
cmns enableThis command has no arguments or keywords.
The CMNS protocol is implicitly enabled whenever an X.25 encapsulation command is included with a serial interface configuration. A particular nonserial interface, however, must be explicitly configured to use CMNS.
Interface configuration
After processing this command on the LAN interfaces (Ethernet, FDDI, and Token Ring), all the X.25-related interface configuration commands are made available.
The following example enables CMNS on interface Ethernet 0:
interface ethernet 0 cmns enable
To exchange datagrams over a serial interface using LAPB encapsulation, use the encapsulation lapb interface configuration command.
encapsulation lapb [dte | dce] [multi | protocol]The default serial encapsulation is HDLC. You must explicitly configure a LAPB encapsulation method.
DTE operation is the default LAPB mode. IP is the default protocol.
Interface configuration
LAPB encapsulations are appropriate only for private connections, where you have complete control over both ends of the link. Connections to X.25 networks should use an x25 encapsulation configuration, which operates the X.25 Layer 3 protocol above a LAPB Layer 2.
One end of the 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.)
Both ends of the LAPB link must specify the same protocol encapsulation.
LAPB encapsulation is supported on serial lines configured for dial-on-demand (DDR) routing. It can be configured on DDR synchronous serial and ISDN interfaces and on DDR dialer rotary groups. It is not supported on asynchronous dialer interfaces.
A single-protocol LAPB encapsulation exchanges datagrams of the given protocol, each in a separate LAPB information frame. You should configure the interface with the protocol-specific parameters needed (for example, a link that carries IP traffic will have an IP address defined for the interface).
A multiprotocol LAPB encapsulation can exchange any or all of the protocols allowed for an serial interface. It also exchanges datagrams, each in a separate LAPB information frame. Since two bytes of protocol identification data precede the protocol data, you do not need to configure the interface with all of the protocol-specific parameters needed for each protocol carried.
Beginning with Cisco IOS Release 11.0, multiprotocol LAPB encapsulation supports transparent bridging. This feature requires use of the encapsulation lapb multi command followed by the bridge-group command, which identifies the bridge group associated with multiprotocol LAPB encapsulation. This feature does not support use of the encapsulation lapb protocol command with a bridge keyword.
Beginning with Release 10.3, LAPB encapsulation supports the priority and custom queueing features.
The following example sets the operating mode as DTE and specifies that AppleTalk protocol traffic will be carried on the LAPB line:
interface serial 1 encapsulation lapb dte appletalk
A dagger (+) indicates that the command is documented in another chapter.
bridge-group+
To specify an serial interface's operation as an X.25 device, use the encapsulation x25 interface configuration command.
encapsulation x25 [dte | dce] [ddn | bfe] | [ietf]| dte | (Optional) Specifies operation as a DTE. This is the default X.25 mode. |
| dce | (Optional) Specifies operation as a DCE. |
| ddn | (Optional) Specifies DDN encapsulation on an interface using DDN X.25 standard service |
| bfe | (Optional) Specifies BFE encapsulation on an interface attached to a Blacker Front End device. Available for BFE operation only. |
| ietf | (Optional) Specifies that the interface's datagram encapsulation should default to use of the IETF standard method, as defined by RFC 1356. |
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.
Interface configuration
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.
The following example configures the interface for connection to a Blacker Front End device:
interface serial 0 encapsulation x25 bfe
To specify a period during which a link will remain connected, even if a brief hardware outage occurs, use the lapb interface-outage interface configuration command.
lapb interface-outage milliseconds| milliseconds | Number of milliseconds a hardware outage can last without having the protocol disconnect the service. The default is 0 milliseconds, which disables this feature. |
0 milliseconds, which disables this feature.
Interface configuration
If a hardware outage lasts longer than the LAPB hardware outage period you select, normal protocol operations will occur. The link will be declared to be down and, when it is restored, a link set up will be initiated.
The following example sets the interface outage period to 100 milliseconds. The link will remain connected for outages equal to or shorter than that period.
encapsulation lapb dte ip lapb interface-outage 100
To specify the maximum permissible number of outstanding frames, called the window size, use the lapb k interface configuration command.
lapb k window-size| window-size | Frame count. It can be a value from 1 to the modulo size minus 1 (the maximum is 7 if the modulo size is 8; it is 127 if the modulo size is 128). The default is 7 frames. |
7 frames
Interface configuration
If the window size is changed while the protocol is up, the new value will take effect only when the protocol is reset. You will be informed that the new value will not take effect immediately.
When using the LAPB modulo 128 mode (extended mode), the window parameter k should be increased to make use of the ability to send a larger number of frames before acknowledgment is required. This is the basis for its ability to achieve greater throughput on high speed links that have a low error rate.
This configured value should match the value configured in the peer X.25 switch. Nonmatching values will cause repeated LAPB REJ frames.
The following example sets the LAPB window size (the k parameter) to ten frames:
interface serial 0 lapb modulo lapb k 10
To specify the LAPB basic (modulo 8) or extended (modulo 128) protocol mode, use the lapb modulo interface configuration command.
lapb modulo modulus| modulus | Either 8 or 128. The value 8 specifies LAPB's basic mode; the value 128 specifies LAPB's extended mode. The default is 8. |
Modulo 8
Interface configuration
The modulo parameter determines which of LAPB's two modes is to be used. The modulo values derive from the fact that basic mode numbers information frames between 0 and 7, whereas extended mode numbers them between 0 and 127. Basic mode is widely available and is sufficient for most links. Extended mode is an optional LAPB feature that may achieve greater throughput on high-speed links that have a low error rate.
The LAPB operating mode may be set on X.25 links as well as LAPB Links. The X.25 modulo is independent of the LAPB layer modulo. Both ends of a link must use the same LAPB mode.
When using modulo 128 mode, the window parameter k should be increased to make use of the ability to send a larger number of frames before acknowledgment is required. This is the basis for its ability to achieve greater throughput on high-speed links that have a low error rate.
If the modulo value is changed while the protocol is up, the new value will take effect only when the protocol is reset. The operator will be informed that the new value will not take effect immediately.
The following example configures a high-speed X.25 link to use LAPB's extended mode:
interface serial 1 encapsulation x25 lapb modulo 128 lapb k 40 clock rate 2000000
To specify the maximum number of bits a frame can hold (the LAPB N1 parameter), use the lapb n1 interface configuration command.
lapb n1 bits| bits | Maximum number of bits in multiples of eight. The minimum and maximum range is dynamically set. Use the ? to view the range. |
The largest (maximum) value available for the particular interface is the default. The Cisco IOS software dynamically calculates n1 whenever you change the maximum transmission unit (MTU), the L2/L3 modulo, or compression on a LAPB interface.
Interface configuration
This command first appeared in Cisco IOS Release 10.0.
 | Caution The LAPB n1 parameter provides little benefit beyond the interface MTU and can easily cause link failures if misconfigured. Cisco recommends that this parameter be left at its default value. |
The Cisco IOS software uses the following formula to determine the minimum n1 value:
(128 (default packet size) + LAPB overhead + X.25 overhead + 2 bytes of CRC) * 8
The Cisco IOS software uses the following formula to determine for the maximum n1 value:
(hardware MTU + LAPB overhead + X.25 overhead + 2 bytes of CRC) * 8
LAPB overhead is 2 bytes for modulo 8 and 3 bytes for modulo 128.
X.25 overhead is 3 bytes for modulo 8 and 4 bytes for modulo 128.
You need not set n1 to an exact value to support a particular X.25 data packet size. The n1 parameter prevents the processing of any huge frames that result from a "jabbering" interface, an unlikely event.
In addition, the various standards bodies specify that n1 be given in bits rather than bytes. While some equipment can be configured in bytes or will automatically adjust for some of the overhead information present, Cisco devices are configured using the true value, in bits, of n1.
You cannot set the n1 parameter to a value less than that required to support an X.25 data packet size of 128 bytes. All X.25 implementations must be able to support 128-byte data packets. Moreover, if you configure n1 to be less than 2104 bits, you receive a warning message that X.25 might have problems because some nondata packets can use up to 259 bytes.
You cannot set the n1 parameter to a value larger than the default unless the hardware MTU size is first increased.
The X.25 software will accept default packet sizes and CALLs that specify maximum packet sizes greater than what the LAPB layer will support, but will negotiate the CALLs placed on the interface to the largest value that can be supported. For switched CALLs, the packet size negotiation takes place end-to-end through the Cisco router so the CALL will not have a maximum packet size that exceeds the capability of either of the two interfaces involved.
The following example shows how to use the ? command to display the minimum and maximum n1 value. In this example, X.25 encapsulation has both the LAPB and X.25 modulo set to 8. Any violation of this n1 range results in an "Invalid input" error message.
interface serial 1 lapb n1 ? <1080-12056> LAPB N1 parameter (bits; multiple of 8)
The following example sets the N1 bits to 16440:
interface serial 0 lapb n1 16440 mtu 2048
A dagger (+) indicates that the command is documented in another chapter.
mtu+
To specify the maximum number of times a data frame can be transmitted (the LAPB N2 parameter), use the lapb n2 interface configuration command.
lapb n2 tries| tries | Transmission count. It can be a value from 1 through 255. The default is 20 transmissions. |
20 transmissions
Interface configuration
The following example sets the N2 tries to 50:
interface serial 0 lapb n2 50
Use the lapb protocol interface configuration command to configure the protocol carried on the LAPB line.
lapb protocol protocol| protocol | Protocol, entered by keyword. It can be one of the following: appletalk, apollo, clns (ISO CLNS), decnet, ip, ipx (Novell IPX), vines, and xns. |
IP
Interface configuration
This command is not available when using a multiprotocol LAPB encapsulation.
The following example sets AppleTalk as the only protocol on the LAPB line:
interface serial 1 encapsulation lapb lapb protocol appletalk
encapsulation lapb
encapsulation lapb-dce
encapsulation lapb-multi
To set the retransmission timer period (the LAPB T1 parameter), use the lapb t1 interface configuration command.
lapb t1 milliseconds| milliseconds | Time in milliseconds. It can be a value from 1 through 64000. The default is 3000 milliseconds. |
3000 milliseconds
Interface configuration
The retransmission timer determines how long a transmitted frame can remain unacknowledged before the LAPB software polls for an acknowledgment. The design of the LAPB protocol specifies that a frame is presumed to be lost if it is not acknowledged within T1; a T1 value that is too small may result in duplicated control information, which can severely disrupt service.
To determine an optimal value for the retransmission timer, use the privileged EXEC command ping to measure the round-trip time of a maximum-sized frame on the link. Multiply this time by a safety factor that takes into account the speed of the link, the link quality, and the distance. A typical safety factor is 1.5. Choosing a larger safety factor can result in slower data transfer if the line is noisy. However, this disadvantage is minor compared to the excessive retransmissions and effective bandwidth reduction caused by a timer setting that is too small.
The following example sets the T1 retransmission timer to 2,000 milliseconds:
interface serial 0 lapb t1 2000
To set the T4 idle timer, after which the router sends out a Poll packet to determine whether the link has suffered an unsignaled failure, use the lapb t4 interface configuration command.
lapb t4 seconds| seconds | Number of seconds between reception of the last frame and the transmission of the outgoing Poll. The default value is 0 seconds, which disables the T4 timer feature. |
0 seconds, which disables the T4 timer feature.
Interface configuration
Any nonzero T4 duration must be greater than T1, the LAPB retransmission timer period.
The following example will poll the other end of an active link if it has been 10 seconds since the last frame was received; if the far host has failed, the service will be declared down after N2 tries are timed out.
interface serial0 encapsulation x25 lapb t4 10
To display X.25 Level 3 parameters for LAN interfaces (such as Ethernet or Token Ring) and other information pertaining to CMNS traffic activity, use the show cmns EXEC command.
show cmns [type number]| type | (Optional) Interface type. |
| number | (Optional) Interface number. |
EXEC
The following is sample output from the show cmns command for an Ethernet interface:
Router# show cmns
Ethernet1 is administratively down, line protocol is down
Hardware address is 0000.0c02.5f4c, (bia 0000.0c2.5f4c), state R1
Modulo 8, idle 0, timer 0, nvc 1
Window size: input 2, output 2, Packet size: input 128, output 128
Timer: TH 0
Channels: Incoming-only none, Two-way 1-4095, Outgoing-only none
RESTARTs 0/0 CALLs 0+0/0+0/0+0 DIAGs 0/0
Table 13-1 describes significant fields shown in the display.
A dagger (+) indicates that the command is documented in another chapter.
show interfaces serial+
To display information about a serial interface, use the show interfaces serial EXEC command.
show interfaces serial number| number | Interface port number. |
EXEC
The following is a partial sample output from the show interfaces serial command for a serial interface using LAPB encapsulation:
Router# show interfaces serial 1
LAPB state is SABMSENT, T1 3000, N1 12056, N2 20, k7,Protocol ip
VS 0, VR 0, RCNT 0, Remote VR 0, Retransmissions 2
IFRAMEs 0/0 RNRs 0/0 REJs 0/0 SABMs 3/0 FRMRs 0/0 DISCs 0/0
Table 13-2 shows the fields relevant to all LAPB connections.
| Parameter | Description |
|---|---|
| LAPB state is | State of the LAPB protocol. |
| T1 3000, N1 12056, ... | Current parameter settings. |
| Protocol | Protocol encapsulated on a LAPB link; this field is not present on interfaces configured for multiprotocol LAPB or X.25 encapsulations. |
| VS | Modulo 8 frame number of the next outgoing I-frame. |
| VR | Modulo 8 frame number of the next I-frame expected to be received. |
| RCNT | Number of received I-frames that have not yet been acknowledged. |
| Remote VR | Number of the next I-frame the remote expects to receive. |
| Retransmissions | Count of current retransmissions due to expiration of T1. |
| Window is closed | No more frames can be transmitted until some outstanding frames have been acknowledged. This message should be displayed only temporarily. |
| IFRAMEs | Count of Information frames in the form of sent/received. |
| RNRs | Count of Receiver Not Ready frames in the form of sent/received. |
| REJs | Count of Reject frames in the form of sent/received. |
| SABMs | Count of Set Asynchronous Balanced Mode commands in the form of sent/received. |
| FRMRs | Count of Frame Reject frames in the form of sent/received. |
| DISCs | Count of Disconnect commands in the form of sent/received. |
The following is a partial sample output from the show interfaces command for a serial X.25 interface:
Router# show interfaces serial 1
X25 address 000000010100, state R1, modulo 8, idle 0, timer 0, nvc 1
Window size: input 2, output 2, Packet size: input 128, output 128
Timers: T20 180, T21 200, T22 180, T23 180, TH 0
Channels: Incoming-only none, Two-way 1-1024, Outgoing-only none
(configuration on RESTART: modulo 8,
Window size: input 2 output 2, Packet size: input 128, output 128
Channels: Incoming-only none, Two-way 5-1024, Outgoing-only none)
RESTARTs 3/2 CALLs 1000+2/1294+190/0+0/ DIAGs 0/0
The stability of the X.25 protocol requires that some parameters not be changed without a RESTART of the protocol. Any change to these parameters will be held until a RESTART is sent or received. If any of these parameters will change, the configuration on RESTART information will be output as well as the values that are currently in effect.
Table 13-3 describes significant fields shown in the display.
| Field | Description |
|---|---|
| X25 address 000000010100 | Address used to originate and accept calls. |
| state R1 | State of the interface. Possible values are:
If the state is R2 or R3, the interface is awaiting acknowledgment of a Restart packet. |
| modulo 8 | Modulo value; determines the packet sequence numbering scheme used. |
| idle 0 | Number of minutes the router waits before closing idle virtual circuits that it originated or accepted. |
| timer 0 | Value of the interface timer, which is zero unless the interface state is R2 or R3. |
| nvc 1 | Default maximum number of simultaneous virtual circuits permitted to and from a single host for a particular protocol. |
| Window size: input 2, output 2 | Default window sizes (in packets) for the interface. The x25 facility interface configuration command can be used to override these default values for the switched virtual circuits originated by the router. |
| Packet size: input 128, output 128 | Default maximum packet sizes (in bytes) for the interface. The x25 facility interface configuration command can be used to override these default values for the switched virtual circuits originated by the router. |
| Timers: T20 180, T21 200, T22 180, T23 180 | Values of the X.25 timers:
|
|
TH0 | Packet acknowledgment threshold (in packets). This value determines how many packets are received before sending an explicit acknowledgment; the default value (0) sends an explicit acknowledgment only when the incoming window is full. |
| Channels: Incoming-only none Two-way 5-1024 Outgoing-only none | Displays the virtual circuit ranges for this interface. |
| RESTARTs 3/2 | Shows RESTART packet statistics for the interface using the format Sent/Received. |
| CALLs 1000+2/1294+190/0+0 | Successful calls sent + failed calls/calls received + calls failed/calls forwarded + calls failed. Calls forwarded are counted as calls sent. |
| DIAGs 0/0 | Diagnostic messages sent+received. |
To display active LLC2 connections, use the show llc2 EXEC command.
show llc2cThis command has no arguments or keywords.
EXEC
The following is sample output from the show llc2 command:
Router# show llc2
TokenRing0 DTE=1000.5A59.04F9,400022224444 SAP=04/04, State=NORMAL
V(S)=5, V(R)=5, Last N(R)=5, Local Window=7, Remote Window=127
ack-max=3, n2=8, Next timer in 7768
xid-retry timer 0/60000 ack timer 0/1000
p timer 0/1000 idle timer 7768/10000
rej timer 0/3200 busy timer 0/9600
ack-delay timer 0/3200
CMNS Connections to:
Address 1000.5A59.04F9 via Ethernet2
Protocol is up
Interface type X25-DCE RESTARTS 0/1
Timers: T10 1 T11 1 T12 1 T13 1
The display includes a CMNS addendum, indicating that LLC2 is running with CMNS. When LLC2 is not running with CMNS, the show llc2 command does not display a CMNS addendum.
Table 13-4 describes significant fields shown in the display.
| Field | Description |
|---|---|
| TokenRing0 | Name of interface on which the session is established. |
| DTE=1000.5A59.04F9, 400022224444 | Address of the station to which the router is talking on this session. (The router's address is the MAC address of the interface on which the connection is established, except when Local Acknowledgment or SDLLC is used, in which case the address used by the router is shown as in this example, following the DTE address and separated by a comma.) |
| SAP=04/04 | Other station's and router's (remote/local) Service Access Point for this connection. The SAP is analogous to a "port number" on the router and allows for multiple sessions between the same two stations. |
| State=
ADM SETUP RESET D_CONN ERROR AWAIT AWAIT_REJ | Current state of the LLC2 session which are any of the following:
Asynchronous Disconnect Mode--A connection is not established, and either end can begin one. Request to begin a connection has been sent to the remote station, and this station is waiting for a response to that request. A previously open connection has been reset because of some error by this station, and this station is waiting for a response to that reset command. This station has requested a normal, expected, end of communications with the remote, and is waiting for a response to that disconnect request. This station has detected an error in communications and has told the other station about it. This station is waiting for a reply to its posting of this error. Connection between the two sides is fully established, and normal communication is occurring. Normal communication state exists, except busy conditions on this station make it such that this station cannot receive information frames from the other station at this time. Out-of-sequence frame has been detected on this station, and this station has requested that the other resend this information Normal communication exists, but this station has had a timer expire, and is trying to recover from it (usually by resending the frame that started the timer). A combination of the AWAIT and BUSY states. A combination of the AWAIT and REJECT states. |
| V(S)=5 | Sequence number of the next information frame this station will send. |
| V(R)=5 | Sequence number of the next information frame this station expects to receive from the other station. |
| Last N (R)=5 | Last sequence number of this station's transmitted frames acknowledged by the remote station. |
| Local Window=7 | Number of frames this station may send before requiring an acknowledgment from the remote station. |
| Remote Window=127 | Number of frames this station can accept from the remote. |
| ack-max=3, n2=8 | Value of these parameters, as given in the previous configuration section. |
| Next timer in 7768 | Number of milliseconds before the next timer, for any reason, goes off. |
| xid-retry timer 0/60000 .... | A series of timer values in the form of next-time/time-between, where "next-time" is the next time, in milliseconds, that the timer will wake, and "time-between" is the time, in milliseconds, between each timer wakeup. A "next-time" of zero indicates that the given timer is not enabled, and will never wake. |
| CMNS Connections to:
Protocol is up Interface type X25-DCE RESTARTS 0/1 Timers: | CMNS addendum when LLC2 is running with the CMNS protocol contains the following:
MAC address of remote station. Up indicates the LLC2 and X.25 protocols are in a state where incoming and outgoing Call Requests can be made on this LLC2 connection. One of the following: X25-DCE, X25-DTE, or X25-DXE (either DTE or DCE). Restarts sent/received on this LLC2 connection. T10, T11, T12, T13 (or T20, T21, T22, T23 for DTE); these are Request packet timers. These are similar in function to X.25 parameters of the same name. |
To display information about configured address maps, use the show x25 map EXEC command.
show x25 mapThis command has no arguments or keywords.
EXEC
The show x25 map command shows information about the following:
The following is sample output from the show x25 map command:
Router# show x25 map
Serial0: X.121 1311001 <--> ip 131.108.170.1
PERMANENT, BROADCAST, 2 VCS: 3 4*
Serial0: X.121 1311005 <--> appletalk 128.1
PERMANENT
Serial1: X.121 1311005 <--> bridge
PERMANENT, BROADCAST
Serial2: X.121 001003 <--> apollo 1.3,
appletalk 1.3,
ip 131.108.1.3,
decnet 1.3,
novell 1.0000.0c04.35df,
vines 00000001:0003,
xns 1.0000.0c04.35df,
clns
PERMANENT, NVC 8, 1 VC: 1024
The display shows that four maps have been configured for the router, two for serial interface 0, one for serial interface 1, and one for the serial interface 2 (which maps eight protocols to the host).
Table 13-5 describes fields shown in the display.
| Field | Description |
|---|---|
| Serial0 | Interface on which this map is configured. |
| X.121 1311001 | X.121 address of the mapped encapsulation host. |
| ip 131.108.170.1 | Type and address of the higher-level protocol(s) mapped to the remote host. Bridge maps do not have a higher-level address; all bridge datagrams are sent to the mapped X.121 address. CLNS maps refer to a configured neighbor as identified by the X.121 address. |
| PERMANENT | Address-mapping type that has been configured for the interface in this entry. Possible values include the following:
|
|
BROADCAST | If any options are configured for an address mapping, they will be listed; the example shows a maps that is configured to forward datagram broadcasts to the mapped host. |
| 2 VCs: | If the map has any active virtual circuits, they are identified. |
| 3 4* | Identifies the circuit number of the active virtual circuits. The asterisk (*) marks the virtual circuit last used to send data.
Note that a single protocol virtual circuit can be associated with a multiprotocol map. |
To display the one-to-one mapping of the host IP addresses and the remote BFE device's IP addresses, use the show x25 remote-red EXEC command.
show x25 remote-redThis command has no arguments or keywords.
EXEC
The following is sample output from the show x25 remote-red command:
Router#show x25 remote-redEntry REMOTE-RED REMOTE-BLACK INTERFACE1 21.0.0.3 21.0.0.7 serial32 21.0.0.10 21.0.0.6 serial13 21.0.0.24 21.0.0.8 serial3
Table 13-6 describes significant fields shown in the display.
| Field | Description |
|---|---|
| Entry | Address mapping entry. |
| REMOTE-RED | Host IP address. |
| REMOTE-BLACK | IP address of the remote BFE device. |
| INTERFACE | Name of interface through which communication with the remote BFE device will take place. |
To display the X.25 routing table, use the show x25 route EXEC command.
show x25 routeThis command has no arguments or keywords.
EXEC
The following is sample output from the show x25 route command:
Router# show x25 route
Number X.121 CUD Forward To
1 1311001 Serial0, 0 uses
2 1311002 131.108.170.10, 0 uses
3 1311003 00 alias Serial0, 2 uses
Table 13-7 describes significant fields shown in the display.
| Field | Description |
|---|---|
| Number | Number identifying the entry in the X.25 routing table. |
| X.121 address | X.121 address pattern associated with this entry. |
| CUD | Call User Data, if any, that has been configured for this route. |
| Forward To | Router interface or IP address to which the router will forward a CALL destined for the X.121 address pattern in this entry.
This field also includes the number of uses of this route. |
To display information about active switched virtual circuits (SVCs) and permanent virtual circuits (PVCs), use the show x25 vc EXEC command.
show x25 vc [lcn]| lcn | (Optional) Logical channel number (LCN). |
EXEC
To examine a particular virtual circuit, add an LCN argument to the show x25 vc command.
This command displays information about virtual circuits that are used for any of the following:
The connectivity information displayed will vary according to the traffic carried by the virtual circuit. For multiprotocol circuits, the output varies depending on the number and identity of the protocols mapped to the X.121 address and the encapsulation method selected for the circuit.
This section provides three sample displays and tables that describe the fields in each display.
The following sample display shows a virtual circuit that is being used to encapsulate traffic between the router and a remote host:
Router# show x25 vc 1024
SVC 1024, State: D1, Interface: Serial0
Started 0:00:31, last input 0:00:31, output 0:00:31
Connects 170090 <-->
compressedtcp 131.108.170.90
ip 131.108.170.90
multiprotocol CUD PID, standard Tx data PID, Reverse charged
Window size input: 2, output: 2
Packet size input: 128, output: 128
PS: 5 PR: 5 ACK: 4 Remote PR: 5 RCNT: 1 RNR: FALSE
Window is closed
Retransmits: 0 Timer (secs): 0 Reassembly (bytes): 0
Held Fragments/Packets: 0/0
Bytes 505/505 Packets 5/5 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0
Table 13-8 describes the general fields shown in the output; Table 13-9 describes the fields specific to encapsulation virtual circuits shown in the output.
| Field | Description |
|---|---|
| SVC 1024 | Identifies the type (switched or permanent) and the number of the virtual circuit. |
| State | State of the virtual circuit (which is independent of the states of other virtual circuits); D1 is the normal ready state. (See the International Telecommunication Union Telecommunication Standardization Sector (ITU-T)1 X.25 Recommendation for a description of virtual circuit states.) |
| Interface | Interface or subinterface on which the virtual circuit is established. |
| Started | Time elapsed since the virtual circuit was created. |
| last input | Time of last input. |
| output | Shows time of last output. |
| Connects...<-->... | Describes the traffic-specific connection information. See Table 13-9, Table 13-10, and Table 13-11 for more information. |
| Window size | Window sizes for the virtual circuit. |
| Packet size | Maximum packet sizes for the virtual circuit. |
| PS | Current send sequence number. |
| PR | Current receive sequence number. |
| ACK | Last acknowledged incoming packet. |
| Remote PR | Last PR number received from the other end of the circuit. |
| RCNT | Count of unacknowledged input packets. |
| RNR | State of the Receiver Not Ready flag; this field is true if the network sends a receiver-not-ready packet. |
| Window is closed | This line appears if the router cannot transmit any more packets until the X.25 layer 3 peer has acknowledged some outstanding packets. |
| Retransmits | Number of times a supervisory packet (RESET or CLEAR) has been retransmitted. |
| Timer | A nonzero time value indicates that a control packet has not been acknowledged yet or that the virtual circuit is being timed for inactivity. |
| Reassembly | Number of bytes received and held for reassembly (packets with the More bit set are reassembled into datagrams for encapsulation virtual circuits; switched X.25 traffic is not reassembled). |
| Held Fragments/Packets | Number of X.25 data fragments to transmit to complete an outgoing datagram, and the number of datagram packets waiting for transmission. |
| Bytes | Total number of bytes sent and received. The Packets, Resets, RNRs, REJs, and INTs fields show the total sent and received packet counts of the indicated types. (RNR is Receiver Not Ready, REJ is Reject, and INT is Interrupt). |
Table 13-9 describes the connection description fields for virtual circuits carrying encapsulation traffic.
| Field | Description |
|---|---|
| 170090 | The X.121 address of the remote host. |
| ip 131.108.170.90 | The higher-level protocol and address values that are mapped to the virtual circuit. |
| multiprotocol CUD PID | Identifies the method used for the protocol identification (PID) in the Call User Data (CUD) field. Since PVCs are not set up using a Call packet, this field is not displayed for encapsulation PVCs. The available methods are as follows:
|
|
standard Tx data PID | Identifies the method used for protocol identification (PID) when sending datagrams. The available methods are as follows:
|
|
Reverse charged | Some important virtual circuit information might be displayed as needed; a DDN IP precedence encapsulation value, reverse charged virtual circuits, and virtual circuits that allow the D-bit procedure. |
The following sample display shows virtual circuits carrying locally switched X.25 traffic:
Router# show x25 vc
PVC 1, State: D1, Interface: Serial2
Started 0:01:26, last input never, output never
PVC <--> Serial1 PVC 1 connected
Window size input: 2, output: 2
Packet size input: 128, output: 128
PS: 0 PR: 0 ACK: 0 Remote PR: 0 RCNT: 0 RNR: FALSE
Retransmits: 0 Timer (secs): 0 Reassembly (bytes): 0
Held Fragments/Packets: 0/0
Bytes 0/0 Packets 0/0 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0
SVC 5, State: D1, Interface: Serial2
Started 0:00:16, last input 0:00:15, output 0:00:15
Connects 170093 <--> 170090 from Serial1 VC 5
Window size input: 2, output: 2
Packet size input: 128, output: 128
PS: 5 PR: 5 ACK: 4 Remote PR: 5 RCNT: 1 RNR: FALSE
Retransmits: 0 Timer (secs): 0 Reassembly (bytes): 0
Held Fragments/Packets: 0/0
Bytes 505/505 Packets 5/5 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0
Table 13-10 lists the connection description fields for virtual circuits carrying locally switched X.25 traffic.
| Field | Description |
|---|---|
| PVC | Flags PVC information. |
| Serial1 PVC 1 | Identifies the other half of a local PVC connection. |
| connected | Identifies the state of the PVC. If the PVC is not connected, the status of the PVC will also be displayed. See Table 13-12 for PVC status messages. |
| 170093 | Identifies the Calling (source) Address of the connection. If a Calling Address Extension was encoded in the call facilities, it will also be displayed. If the source host is a CMNS host, its MAC address will also be displayed. |
| 170090 | Identifies the Called (destination) Address of the connection. If a Called Address Extension was encoded in the call facilities, it will also be displayed. If the destination host is a CMNS host, its MAC address will also be displayed. |
| from Serial1 VC 5 | Indicates the direction of the call ("from" or "to") and the connecting interface and virtual circuit number. |
The following sample display shows virtual circuits carrying remotely switched X.25 traffic.
Router# show x25 vc
PVC 2, State: D1, Interface: Serial2
Started 0:01:25, last input never, output never
PVC <--> [131.108.165.92] Serial2/0 PVC 1 connected
XOT between 131.108.165.91, 1998 and 131.108.165.92, 27801
Window size input: 2, output: 2
Packet size input: 128, output: 128
PS: 0 PR: 0 ACK: 0 Remote PR: 0 RCNT: 0 RNR: FALSE
Retransmits: 0 Timer (secs): 0 Reassembly (bytes): 0
Held Fragments/Packets: 0/0
Bytes 0/0 Packets 0/0 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0
SVC 6, State: D1, Interface: Serial2
Started 0:00:04, last input 0:00:04, output 0:00:04
Connects 170093 <--> 170090 from
XOT between 131.108.165.91, 1998 and 131.108.165.92, 27896
Window size input: 2, output: 2
Packet size input: 128, output: 128
PS: 5 PR: 5 ACK: 4 Remote PR: 5 RCNT: 1 RNR: FALSE
Retransmits: 0 Timer (secs): 0 Reassembly (bytes): 0
Held Fragments/Packets: 0/0
Bytes 505/505 Packets 5/5 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0
Table 13-11 lists the connection description fields for virtual circuits carrying remotely switched X.25 traffic.
| Field | Description |
|---|---|
| PVC | Flags PVC information. |
| [131.108.165.92] | Indicates the IP address of the router remotely connecting the PVC. |
| Serial 2/0 PVC 1 | Identifies the remote interface and PVC number. |
| connected | Identifies the state of the PVC. If the PVC is not connected, the status of the PVC will also be displayed. See Table 13-12 for the PVC status messages. |
| 170093 | Identifies the Calling (source) Address of the connection. If a Calling Address Extension was encoded in the call facilities, it will also be displayed. |
| 170090 | Identifies the Called (destination) Address of the connection. If a Called Address Extension was encoded in the call facilities, it will also be displayed. |
| from | Indicates the direction of the call ("from" or "to"). |
| XOT between... | Identifies the IP addresses and port numbers of the XOT connection. |
Table 13-12 lists the PVC states that can be reported. These states are also reported by the debug x25 command in PVC-SETUP packets (for remote PVCs only) as well as in the PVCBAD system error message. Some states apply only to remotely switched PVCs.
| Field | Description |
|---|---|
| waiting to connect | The PVC is waiting to be processed for connecting. |
| dest. disconnected | The other end disconnected the PVC. |
| PVC/TCP connection refused | A remote PVC XOT TCP connection was tried and refused. |
| PVC/TCP routing error | A remote PVC XOT TCP connection routing error was reported. |
| PVC/TCP connect timed out | A remote PVC XOT TCP connection attempt timed out. |
| trying to connect via TCP | A remote PVC XOT TCP connection is established and is in the process of connecting. |
| awaiting PVC-SETUP reply | A remote PVC has initiated an XOT TCP connection and is waiting fro a reply to the setup message. |
| connected | The PVC is up. |
| no such dest. interface | The remote destination interface was reported to be in error by the remote router. |
| dest interface is not up | The target interface's X.25 service is down. |
| non-X.25 dest. interface | The target interface isn't configured for X.25. |
| no such dest. PVC | The targeted PVC does not exist. |
| dest PVC config mismatch | The targeted PVC is already connected. |
| mismatched flow control values | The configured flow control values do not match. |
| can't support flow control values | The window sizes or packet sizes of the PVC cannot be supported by one of its two interfaces. |
To configure the router to accept all reverse charge calls, use the x25 accept-reverse interface configuration command. To disable this facility, use the no form of this command.
x25 accept-reverseThis command has no arguments or keywords.
Disabled
Interface configuration
This command causes the interface to accept reverse charge calls by default. This behavior also can be configured on a per-peer basis using the x25 map interface configuration command.
The following example sets acceptance of reverse charge calls:
interface serial 0 x25 accept-reverse
To set the X.121 address of a particular network interface, use the x25 address interface configuration command.
x25 address x.121-address| x.121-address | Variable-length X.121 address. The address is assigned by the X.25 network service provider. |
DDN and BFE encapsulations have a default interface address generated from the interface IP address; for proper DDN or BFE operation, this generated X.121 address should not be changed. Standard X.25 encapsulations do not have a default.
Interface configuration
When connecting to a PDN, the PDN administration will assign the X.121 address that should be used. Other applications (for example, a private X.25 service), may assign arbitrary X.121 addresses as required by the network and service design. X.25 interfaces that only engage in X.25 switching do not need to assign an X.121 address.
The following example sets the X.121 address for the interface:
interface serial 0 encapsulation x25 x25 address 00000123005
The address must match that assigned by the X.25 network service provider.
To specify how a router configured for x25 bfe-emergency decision will participate in emergency mode, use the x25 bfe-decision interface configuration command.
x25 bfe-decision {no | yes | ask}| no | Prevents the router from participating in emergency mode and from sending address translation information to the BFE device. |
| yes | Allows the router to participate in emergency mode and to send address translation information to the BFE when the BFE enters emergency mode. The router obtains this information from the table created by the x25 remote-red command. |
| ask | Configures the router to prompt the console operator to enter the bfe EXEC command. |
The router does not participate in emergency mode.
Interface configuration
The following example configures interface Serial 0 to require an EXEC command from the administrator before it participates in emergency mode. The host IP address is 21.0.0.12, and the address of the remote BFE unit is 21.0.0.1. When the BFE enters emergency mode, the router will prompt the administrator for EXEC command bfe enter to direct the router to participate in emergency mode.
interface serial 0 x25 bfe-emergency decision x25 remote-red 21.0.0.12 remote-black 21.0.0.1 x25 bfe-decision ask
bfe
x25 bfe-emergency
x25 remote-red
To configure the circumstances under which the router participates in emergency mode, use the x25 bfe-emergency interface configuration command.
x25 bfe-emergency {never | always | decision}The router does not send address translation information to the BFE.
Interface configuration
The following example configures interface Serial 0 to require an EXEC command from the administrator before it participates in emergency mode. The host IP address is 21.0.0.12, and the address of the remote BFE unit is 21.0.0.1. When the BFE enters emergency mode, the router will prompt the administrator for EXEC command bfe enter to direct the router to participate in emergency mode.
interface serial 0 x25 bfe-emergency decision x25 remote-red 21.0.0.12 remote-black 21.0.0.1 x25 bfe-decision ask
To set a default protocol, use the x25 default interface configuration command. To remove the default protocol specified, use the no form of this command.
x25 default protocol| protocol | Specifies the protocol to assume; may be ip or pad. |
No default protocol is set.
Interface configuration
This command specifies the protocol assumed by the router for incoming calls with unknown or missing Call User Data. If you do not use the x25 default interface configuration command, the router clears any incoming calls with unrecognized Call User Data.
The following example establishes IP as the default protocol for X.25 calls:
interface serial 0 x25 default ip
To force facilities on a per-call basis for calls originated by the router (switched calls are not affected), use the x25 facility interface configuration command. To disable a facility, use the no form of this command.
x25 facility facility-keyword value| facility-keyword | User facility. |
| value | Facility value; see Table 13-13 for a list of supported facilities and their values. |
No facility is sent.
Interface configuration
Table 13-13 lists X.25 user facilities.
The following example specifies a transit delay value in an X.25 configuration:
interface serial 0 x25 facility transit-delay 24000
The following example sets an RPOA name and then send the list via the X.25 user facilities:
x25 rpoa green_list 23 35 36 interface serial 0 x25 facility rpoa green_list
To set the highest incoming-only virtual circuit number, use the x25 hic interface configuration command.
x25 hic circuit-number| circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no incoming-only virtual circuit range. The default is 0. |
0
Interface configuration
This command is applicable only if you have the X.25 switch configured for an incoming only virtual circuit range. Incoming is from the perspective of the X.25 DTE. If you do not want any outgoing calls from your DTE, configure both ends to disable the two-way range (set ltc and htc to 0) and configure an incoming-only range. Any incoming-only range must come before (that is, must be numerically less than) any two-way range. Any two-way range must come before any outgoing-only range.
The following example sets a valid incoming-only virtual circuit range of 1 to 5:
interface serial 0 x25 lic 1 x25 hic 5 x25 ltc 6
To set the highest outgoing-only virtual circuit number, use the x25 hoc interface configuration command.
x25 hoc circuit-number| circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no outgoing-only virtual circuit range. The default is 0. |
0
Interface configuration
This command is applicable only if you have the X.25 switch configured for an outgoing only virtual circuit range. Outgoing is from the perspective of the X.25 DTE. If you do not want any incoming calls on your DTE, disable the two-way range (set the values of x25 ltc and x25 htc to 0) and configure an outgoing-only range. Any outgoing-only range must come after (that is, be numerically greater than) any other range.
The following example sets a valid outgoing-only virtual circuit range of 2000 to 2005:
interface serial 0 x25 loc 2000 x25 hoc 2005
To set the maximum number of packets to hold until a virtual circuit is able to transmit, use the x25 hold-queue interface configuration command. To remove this command from the configuration file and restore the default value, use the no form of this command without an argument.
x25 hold-queue packets| packets | Number of packets. A hold queue value of 0 allows an unlimited number of packets in the hold queue. This argument is optional for the no form of this command. The default is 10 packets. |
10 packets
Interface configuration
If you set the queue-size to 0 when using the no x25 hold-queue command, there will be no hold queue limit. While this will prevent drops until the router runs out of memory, it is only rarely appropriate. A virtual circuit hold queue value is determined when it is created; changing this parameter will not affect the hold queue limits of the existing virtual circuits.
The following example sets the X.25 hold queue to hold 25 packets:
interface serial 0 x25 hold-queue 25
A dagger (+) indicates that the command is documented in another chapter.
To start the timer that prevents additional calls to a destination for a given period of time (thus preventing overruns on some X.25 switches caused by Call Request packets), use the x25 hold-vc-timer interface configuration command. To restore the default value for the timer, use the no form of this command
x25 hold-vc-timer minutes| minutes | Number of minutes to prevent calls from going to a previously failed destination. Incoming calls will still be accepted. The default is 0 minutes. |
0 minutes
Interface configuration
Only Call Requests that the router originates will be held down; routed X.25 Call Requests are not affected by this parameter.
Upon receiving a Clear Request for an outstanding Call Request, the X.25 support code immediately tries another Call Request if it has more traffic to send, and this action might cause overrun problems.
The failed virtual circuits can be observed with the show x25 vc command; they are renumbered to the illegal value 4096 and have the nonstandard state X1.
The following example sets this timer to 3 minutes:
interface serial 0 x25 hold-vc-timer 3
To set the highest two-way virtual circuit number, use the x25 htc interface configuration command.
x25 htc circuit-number| circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no two-way virtual circuit range. The default is 1024 for X.25 network service interfaces; 4095 for CMNS network service interfaces. |
1024 for X.25 network service interfaces; 4095 for CMNS network service interfaces.
Interface configuration
This command is applicable if the X.25 switch is configured for a two-way virtual circuit range. Any two-way virtual circuit range must come after (that is, be numerically larger than) any incoming-only range, and must come before any outgoing-only range.
The following example sets a valid two-way virtual circuit range of 5 to 25:
interface serial 0 x25 ltc 5 x25 htc 25
To define the period of inactivity after which the router can clear a switched virtual circuit (SVC), use the x25 idle interface configuration command.
x25 idle minutes| minutes | Idle period in minutes. The default is 0, which causes the router to keep the SVC open indefinitely. |
0 (causes the router to keep the SVC open indefinitely)
Interface configuration
Calls originated and terminated by the router are cleared; PAD and switched virtual circuits are not affected. To clear one or all virtual circuits at once, use the privileged EXEC command clear x25-vc.
The following example sets a 5-minute wait period before an idle circuit is cleared:
interface serial 2 x25 idle 5
To enable the router to use the IP precedence value when it opens a new virtual circuit, use the x25 ip-precedence interface configuration command. To cause the precedence value to be ignored when opening virtual circuits, use the no form of this command.
x25 ip-precedenceThis command has no arguments or keywords.
The routers open one virtual circuit for all types of service.
Interface configuration
This feature is useful only for DDN or BFE encapsulations, because only these methods have an IP precedence facility defined to allow the source and destination devices to both use the virtual circuit for traffic of the given IP priority.
There is a problem associated with this feature in that some hosts send nonstandard data in the IP TOS field, thus causing multiple wasteful virtual circuits to be created.
Four virtual circuits may be opened based on IP precedence to encapsulate routine, priority, immediate, and all higher precedences.
The x25 map nvc limit or the default x25 nvc limit still applies.
The following example allows new IP encapsulation virtual circuits based on the IP precedence:
interface serial 3 x25 ip-precedence
To set the interface default maximum input packet size to match that of the network, use the x25 ips interface configuration command.
x25 ips bytes| bytes | Byte count. It can be one of the following values: 16, 32, 64, 128, 256, 512, 1024, 2048, or 4096. The default is 128 bytes. |
128 bytes
Interface configuration
X.25 network connections have a default maximum input packet size set by the network administrator. Larger packet sizes require less overhead processing. To send a packet larger than the X.25 packet size over an X.25 virtual circuit, a router must break the packet into two or more X.25 packets with the M-bit ("more data" bit) set. The receiving device collects all packets with the M-bit set and reassembles the original packet.
The following example sets the default maximum packet sizes to 512:
interface serial 1 x25 ips 512 x25 ops 512
To set the lowest incoming-only virtual circuit number, use the x25 lic interface configuration command.
x25 lic circuit-number| circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no incoming-only virtual circuit range. The default is 0. |
0
Interface configuration
This command is applicable only if you have the X.25 switch configured for an incoming only virtual circuit range. Outgoing is from the perspective of the X.25 DTE. If you do not want any incoming calls on your DTE, disable the two-way range (set the values of x25 ltc and x25 htc to 0) and configure an outgoing-only range. Any outgoing-only range must come after (that is, be numerically greater than) any other range.
This command is applicable if you have the X.25 switch configured for two way virtual circuit range.
The following example sets a valid incoming-only virtual circuit range of 1 to 5 and sets the lowest two-way virtual circuit number:
interface serial 0 x25 lic 1 x25 hic 5 x25 ltc 6
To force X.25 Level 3 (packet-level) to restart when Level 2 (LAPB, the link level) resets, use the x25 linkrestart interface configuration command. To disable this function, use the no form of this command.
x25 linkrestartThis command has no arguments or keywords.
Forcing packet-level restarts is the default and is necessary for networks that expect this behavior.
Interface configuration
The following example disables the link level restart:
interface serial 3 no x25 linkrestart
To set the lowest outgoing-only virtual circuit number, use the x25 loc interface configuration command.
x25 loc circuit-number| circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no outgoing-only virtual circuit range. The default is 0. |
0
Interface configuration
This command is applicable only if you have the X.25 switch configured for an outgoing only virtual circuit range. Outgoing is from the perspective of the X.25 DTE. If you do not want any incoming calls from your DTE, configure the values of x25 loc and x25 hoc and set the values of x25 ltc and x25 htc to 0.
The following example sets a valid outgoing-only virtual circuit range of 2000 to 2005:
interface serial 0 x25 loc 2000 x25 hoc 2005
To set the lowest two-way virtual circuit number, use the x25 ltc interface configuration command.
x25 ltc circuit-number| circuit-number | Virtual circuit number from 1 through 4095, or 0 if there is no two-way virtual circuit range. The default is 1. |
1
Interface configuration
This command is applicable if you have the X.25 switch configured for a two-way virtual circuit range. Any two-way virtual circuit range must come after (that is, be numerically larger than) any incoming-only range, and must come before any outgoing-only range.
The following example sets a valid two-way virtual circuit range of 5 to 25:
interface serial 0 x25 ltc 5 x25 htc 25
To set up the LAN protocols-to-remote host mapping, use the x25 map interface configuration command. To retract a prior mapping, use the no form of this command with the appropriate network protocol(s) and X.121 address argument.
x25 map protocol address [protocol2 address2[...[protocol9 address9]]] x.121-address [option]| protocol | Protocol type, entered by keyword. Supported protocols are entered by keyword, as listed in Table 13-14. As many as nine protocol and address pairs can be specified in one command line. |
| address | Protocol address. |
| x.121-address | X.121 address of the remote host. |
| option | (Optional) Provides additional functionality or allows X.25 facilities to be specified for originated calls. Can be any of the options listed in Table 13-15. |
No LAN protocol-to-remote host mapping is set up.
Interface configuration
Because no defined protocol can dynamically determine LAN protocol-to-remote host mappings, you must enter all of the information for each host with which the router may exchange X.25 encapsulation traffic.
Two methods are available to encapsulate traffic, Cisco's long-available encapsulation method and the IETF's standard method (defined in RFC 1356); the latter allows hosts to exchange several protocols over a single virtual circuit. Cisco's encapsulation method is the default (for backward compatibility, unless the interface configuration command specifies ietf.
When you configure multiprotocol maps, you can specify a maximum of nine protocol and address pairs in an x25 map command. However, you can specify a protocol once only. For example, you can specify the IP protocol and an IP address, but you cannot specify another IP address. If compressedtcp and ip are both specified, the same IP address must be used.
Bridging is supported only using Cisco's traditional encapsulation method. For correct operation, bridging maps must specify the broadcast option.
Since most datagram routing protocols rely on broadcasts or multicasts to send routing information to their neighbors, the broadcast keyword is needed to run such routing protocols over X.25.
Encapsulation maps might also specify that traffic between the two hosts should be compressed, thus increasing the effective bandwidth between them at the expense of memory and computation time. Each compression virtual circuit requires memory and computation resources, so compression should be used with care and monitored to maintain acceptable resource usage and overall router performance.
OSPF treats a nonbroadcast, multiaccess network such as X.25 much the same way it treats a broadcast network in that it requires selection of a designated router. In previous releases, this required manual assignment in the OSPF configuration using the neighbor interface router configuration command. When the x25 map command is included in the configuration with the broadcast, and the ip ospf network command (with the broadcast keyword) is configured, there is no need to configure any neighbors manually. OSPF will now run over the X.25 network as a broadcast network. (Refer to the ip ospf network interface command for more detail.)
You can modify the options of an x25 map command by restating the complete set of protocols and addresses specified for the map, followed by the desired options. To delete a map command, you must also specify the complete set of protocols and addresses; the options can be omitted when deleting a map.
Once defined, a map's protocols and addresses cannot be changed; this is because the router cannot determine whether you want to add to, delete from, or modify an existing map's protocol and address specification (or simply mistyped the command). To change a map's protocol and address specification, you must delete it and create a new map.
A given protocol/address pair cannot be used in more than one map on the same interface.
Table 13-14 lists the protocols supported by X.25.
| Keyword | Protocol |
|---|---|
| apollo | Apollo Domain |
| appletalk | AppleTalk |
| bridge | Bridging1 |
| clns | ISO Connectionless Network Service |
| cmns | ISO Connection-Mode Network Service2 |
| compressedtcp | TCP header compression |
| decnet | DECnet |
| ip | IP |
| ipx | Novell IPX |
| pad | PAD links3 |
| qllc | SNA encapsulation in X.254 |
| vines | Banyan VINES |
| xns | XNS |
Table 13-15 lists the map options supported by X.25.
The following example maps IP address 131.08.2.5 to X.121 address 000000010300. The broadcast keyword directs any broadcasts sent through this interface to the specified X.121 address.
interface serial 0 x25 map ip 131.08.2.5 000000010300 broadcast
The following example specifies an RPOA name to be used when originating connections:
x25 rpoa green_list 23 35 36 interface serial 0 x25 map ip 131.108.170.26 10 rpoa green_list
The following example specifies a network user identifier (NUID) facility to send on calls originated for the address map:
interface serial 0 x25 map IP 131.108.174.32 2 nudata "Network User ID 35"
Strings can be quoted, but quotation marks are not required unless embedded blanks are present.
A dagger (+) indicates that the command is documented in another chapter.
ip ospf network+
show x25 map
x25 facility
x25 map bridge
x25 map cmns
x25 map compressedtcp
x25 rpoa
To configure an Internet-to-X.121 address mapping for bridging over X.25, use the x25 map bridge interface configuration command.
x25 map bridge x.121-address broadcast [option]| x.121-address | The X.121 address. |
| broadcast | Required keyword for bridging over X.25. |
| option | (Optional) Services that can be added to this map; the same options as the x25 map command; see Table 13-15. |
No bridging over X.25 is configured.
Interface configuration
The following example configures bridging of X.25 frames using a maximum of six virtual circuits:
interface serial 1 x25 map bridge 000000010300 broadcast nvc 6
To map NSAP addresses to either MAC-layer addresses or X.121 addresses after enabling CMNS on a nonserial interface, use the x25 map cmns interface configuration command. To retract a mapping, use the no form of this command with the appropriate address arguments.
x25 map cmns nsap mac-address| nsap | NSAP address. The NSAP can be either the actual DTE NSAP address or the prefix of the NSAP address. The NSAP prefix is sufficient for a best match to route a call. |
| mac-address | MAC-level address. |
| x.121-address | (Optional) X.121 address. |
No mapping is configured.
Interface configuration
The address arguments specify the NSAP address-to-MAC address or NSAP address-to-X.121 address mappings. A mapping to a MAC address is only valid on a nonserial interface. A mapping to an X.121 address is only valid on a serial interface.
If a received call has a destination NSAP, the list of CMNS hosts is consulted and, if an NSAP (or NSAP preamble) match is found, the call is routed according to the best fit (which, depending on the map configuration, may be out either a CMNS or an X.25 interface). If no NSAP match is found, the call is handled according to its X.121 address for routing or acceptance as an encapsulation call.
The following example switches traffic intended for any NSAP address with prefix 38.8261.17 to MAC address 0000.0C02.5F56 over interface Ethernet 0:
interface ethernet 0 cmns enable x25 map cmns 38.8261.17 0000.0C02.5F56
To map compressed TCP traffic to an X.121 address, use the x25 map compressedtcp interface configuration command. To delete a TCP header compression map for the link, use the no form of this command.
x25 map compressedtcp address x.121-address [option]| address | IP address. |
| x.121-address | X.121 address. |
| option | (Optional) The same options as those for the x25 map command; see Table 13-15. |
No mapping is configured.
Interface configuration
TCP header compression is supported over X.25 links. The implementation of compressed TCP over X.25 uses a virtual circuit (VC) to pass the compressed packets. IP traffic (including standard TCP) uses separate virtual circuits. The nvc map option cannot be used for TCP header compression, as only one VC can carry compressed TCP header traffic to a given host.
The following example establishes a map for TCP header compression on interface serial 4:
interface serial 4 ip tcp header-compression x25 map compressedtcp 131.108.2.5 000000010300
To configure an X.121 address mapping for packet assembler/disassembler (PAD) access over X.25, use the x25 map pad interface configuration command.
x25 map pad x.121-address [option]| x.121-address | X.121 address of the interface. |
| option | (Optional) Services that can be added to this map--the same options as the x25 map command (see Table 13-15). |
No specific options are used for PAD access.
Interface configuration
Use a PAD map to configure optional X.25 facility use for PAD access. When used with the x25 pad-access interface configuration command, the x25 map pad command restricts incoming PAD access to those mapped hosts.
The following example configures an X.25 interface to restrict incoming PAD access to the single mapped host. This example requires that both incoming and outgoing PAD access use the network user identification (NUID) user authentication.
interface serial 1 x25 pad-access x25 map pad 000000010300 nuid johndoe secret
To set the window modulus, use the x25 modulo interface configuration command.
x25 modulo modulus| modulus | Either 8 or 128. The value of the modulo parameter must agree with that of the device on the other end of the X.25 link. The default is 8. |
8
Interface configuration
X.25 supports flow control with a sliding window sequence count. The window counter restarts at zero upon reaching the upper limit, which is called the window modulus. Modulo 128 operation is also referred to as extended packet sequence numbering, which allows larger packet windows.
The following example sets the window modulus to 128:
interface serial 0 x25 modulo 128
x25 facility windowsize
x25 win
x25 wout
To specify the maximum number of switched virtual circuits (SVCs) that a protocol can have open simultaneously to one host, use the x25 nvc interface configuration command. To increase throughput across networks, you can establish up to eight switched virtual circuits to a host/protocol.
x25 nvc count| count | Circuit count from 1 to 8. A maximum of eight virtual circuits can be configured for each protocol/host pair. Protocols that do not tolerate out-of-order delivery, such as encapsulated TCP header compression, will only use one virtual circuit despite this value. The default is 1. Permitting more than one SVC may help throughput on slow networks. |
1
Interface configuration
When the windows and output queues of all existing connections to a host are full, a new virtual circuit will be opened to the designated circuit count. If a new connection cannot be opened, the data is dropped.
The following example sets the default maximum number of switched virtual circuits that each map can open simultaneously to 4:
interface serial 0 x25 nvc 4
To set the interface default maximum output packet size to match that of the network, use the x25 ops interface configuration command.
x25 ops bytes| bytes | Byte count that is one of the following: 16, 32, 64, 128, 256, 512, 1024, 2048, or 4096. The default is 128 bytes. |
128 bytes
Interface configuration
X.25 networks use maximum output packet sizes set by the network administration. Larger packet sizes are better because smaller packets require more overhead processing. To send a packet larger than the X.25 packet size over an X.25 virtual circuit, a router must break the packet into two or more X.25 packets with the M-bit ("more data" bit) set. The receiving device collects all packets with the M-bit set and reassembles the original packet.
The following example sets the default maximum packet sizes to 512:
interface serial 1 x25 ips 512 x25 ops 512
Use the x25 pad-access interface configuration command to cause the packet assembler/disassembler (PAD) software to accept PAD connections only from statically mapped X.25 hosts.
x25 pad-accessThis command has no arguments or keywords.
Accept PAD connections from any host.
Interface configuration
By default, all PAD connection attempts are processed for session creation or protocol translation, subject to the configuration of those functions. If you use the x25 pad-access command, PAD connections are processed only for incoming calls with a source address that matches a statically mapped address configured with the x25 map pad interface configuration command. PAD connections are refused for any incoming calls with a source address that has not been statically mapped.
The following example restricts incoming PAD access on the interface to attempts from the host with the X.121 address 000000010300:
interface serial 1 x25 pad-access x25 map pad 000000010300
service pad
x25 map pad
To establish an encapsulation permanent virtual circuit (PVC), use the encapsulating version of the x25 pvc interface configuration command. To delete the PVC, use the no form of this command with the appropriate channel number.
x25 pvc circuit protocol address [protocol2 address2[...[protocol9 address9]]] x.121-address| circuit | Virtual-circuit channel number, which must be less than the virtual circuits assigned to the switched virtual circuits (SVCs). |
| protocol | Protocol type, entered by keyword. Supported protocols are listed in Table 13-16. As many as nine protocol and address pairs can be specified in one command line. |
| address | Protocol address of the host at the other end of the PVC. |
| x.121-address | X.121 address. |
| option | (Optional) Provides additional functionality or allows X.25 parameters to be specified for the PVC. Can be any of the options listed in Table 13-17. |
No encapsulation PVC is established. The PVC window and maximum packet sizes default to the interface default values.
Interface configuration
PVCs are not supported for ISO CMNS.
You no longer need to specify a datagram protocol/address mapping before you can set up a PVC; a map is implied from the PVC configuration. Configurations generated by the router will no longer specify a map for encapsulating PVCs.
An X.121 address must be specified for the PVC, much as is done for an x25 map command, although the address does not appear in the PVC data exchange. When configuring a PVC to carry CLNS traffic, the X.121 address is used as the SNPA to associate the PVC with a CLNS neighbor configuration.
Table 13-16 lists supported protocols.
| Keyword | Protocol |
|---|---|
| apollo | Apollo Domain |
| appletalk | AppleTalk |
| bridge | Bridging 1 |
| clns | OSI Connectionless Network Service |
| compressedtcp | TCP header compression |
| decnet | DECnet |
| ip | IP |
| ipx | Novell IPX |
| qllc | SNA encapsulation in X.252 |
| vines | Banyan VINES |
| xns | XNS |
Table 13-17 lists supported X.25 PVC options.
The following example establishes a PVC on channel 2 to encapsulate VINES and IP with the far host:
interface serial 0 x25 ltc 5 x25 pvc 2 vines 60002A2D:0001 ip 131.108.170.91 11110001
To configure a switched permanent virtual circuit (PVC) for a given interface, use the switched version of the x25 pvc interface configuration command.
x25 pvc number1 interface type number pvc number2 [option]| number1 | PVC number that will be used on the local interface (as defined by the primary interface command). |
| interface | Required keyword to specify an interface. |
| type | Remote interface type. |
| number | Remote interface number. |
| pvc | Required keyword to specify a switched PVC. |
| number2 | PVC number that will be used on the remote interface. |
| option | (Optional) Adds certain features to the mapping specified; can be either option listed in Table 13-18. |
No switched PVC is configured. The PVC window and maximum packet sizes default to the interface default values.
Interface configuration
You can configure X.25 PVCs in the X.25 switching software. This means that DTEs that require permanent circuits can be connected to the router acting as an X.25 switch and have a properly functioning connection. X.25 RESETs will be sent to indicate when the circuit comes up or goes down.
PVC circuit numbers must come before (that is, be numerically smaller than the circuit numbers allocated to any SVC range).
Table 13-18 lists the switched PVC options supported by X.25.
The following example configures a PVC connected between two serial interfaces on the same router. In this type of interconnection configuration, the alternate interface must be specified along with the PVC number on that interface. To make a working PVC connection, two commands must be specified, each pointing to the other as this example illustrates.
interface serial 0 encapsulation x25 x25 ltc 5 x25 pvc 1 interface serial 1 pvc 1 interface serial 1 encapsulation x25 x25 ltc 5 x25 pvc 1 interface serial 0 pvc 1
To connect two permanent virtual circuits (PVCs) across a TCP/IP LAN, use the tunnel version of the x25 pvc interface configuration command.
x25 pvc number1 tunnel address interface serial string pvc number2 [option]| number1 | PVC number of the connecting device. |
| tunnel | Indicates two PVCs will be connected across a TCP/IP LAN. |
| address | IP address of the router to which you are connecting. |
| interface serial | Indicates the interface is serial. |
| string | Serial interface specification that accepts either a number or a string in model 7000 format (number/number) to denote the serial interface. |
| pvc | Indicates a PVC. |
| number2 | Remote PVC number on the target interface. |
| option | (Optional) Adds certain features for the connection; can be either option listed in Table 13-19. |
No PVCs are connected across a TCP/IP LAN. The PVC window and packet sizes default to the interface default values.
Interface configuration
Use the PVC tunnel commands to tell the Cisco IOS software to what the far end of the PVC is connected. The incoming and outgoing packet sizes and window sizes must match the remote PVC outgoing and incoming sizes.
Each X.25-over-TCP (XOT) connection relies on a TCP session to carry traffic. To ensure that these TCP sessions remain connected in the absence of XOT traffic, use the service tcp-keepalives-in and service tcp-keepalives-out global configuration commands. If TCP keepalives are not enabled, XOT permanent virtual circuits (PVCs) might encounter problems if one end of the connection is reloaded. When the reloaded host attempts to establish a new connection, the other host refuses the new connection because it has not been informed that the old session is no longer active. Recovery from this state requires the other host to be informed that its TCP session is no longer viable so that it attempts to reconnect the PVC.
Also, TCP keepalives inform a router when an XOT switched virtual circuit (SVC) session is not active, thus freeing the router's resources.
Table 13-19 lists the PVC tunnel options supported by X.25.
The following example enters the parameters for one side of a connection destined for a router platform other than the Cisco 7000 series:
service tcp-keepalives-inservice tcp-keepalives-outinterface serial 0x25 pvc 1 tunnel 131.108.1.2 interface serial 1 pvc 2
The following example enters the parameters for one side of a connection destined for the Cisco 7000 series:
service tcp-keepalives-inservice tcp-keepalives-outinterface serial 0x25 pvc 1 tunnel 131.108.1.2 interface serial 1/1 pvc 2
See the section "X.25 and LAPB Configuration Examples" in the Router Products Configuration Guide for more complete configuration examples.
A dagger (+) indicated that a command is documented outside this chapter.
service tcp-keepalives-in +
service tcp-keepalives-out +
To set up the table that lists the Blacker Front End (BFE) nodes (host or gateways) to which the router will send packets, use the x25 remote-red interface configuration command.
x25 remote-red host-ip-address remote-black blacker-ip-address| host-ip-address | IP address of the host or a router that the packets are being sent to. |
| remote-black | Delimits the addresses for the table being built. |
| blacker-ip-address | IP address of the remote BFE device in front of the host to which the packet is being sent. |
No table is set up.
Interface configuration
The table that results from this command provides the address translation information the router sends to the BFE when it is in emergency mode.
The following example sets up a short table of BFE nodes for interface serial 0:
interface serial 0 x25 remote-red 131.108.9.3 remote-black 131.108.9.13 x25 remote-red 192.108.15.1 remote-black 192.108.15.26
x25 bfe-decision
show x25 remote-red
To create an entry in the X.25 routing table, use the x25 route global configuration command. To remove an entry from the table, use a no form of the command.
x25 route [#position] x.121-address [cud pattern] interface type number| #position | (Optional) A pound sign (#) followed by a number to designate a positional parameter at which to insert the new entry. If no position parameter is given, the entry is appended to the end of the routing table. |
| x.121-address | Called X.121 address pattern. This argument can be either an actual X.121 destination address or a regular expression such as 1111*, representing a group of X.121 addresses. |
| cud pattern | (Optional) Call User Data pattern, which is specified as a printable ASCII string. The Call User Data field may be present in a call packet and is commonly 4 bytes long. |
| interface type number | Keyword and destination interface type and unit or port number; for example, interface Ethernet 0. |
| ip address | Keyword and IP address of the network interface or DTE for connections routed through a LAN. Optionally, up to five alternate IP addresses can be listed and each in turn will be tried in the event that the first destination fails, thus allowing alternate routes and decreasing the likelihood of failure. |
| xot-source type number | (Optional) X.25-over-TCP (XOT). Keyword and interface type unit or port number (for example, Loopback 0) to be used as the source address of a TCP connection, allowing the connection to move to a backup interface without terminating the TCP session. |
| xot-keepalive-period n | X.25-over-TCP (XOT). Specifies the TCP keepalive period.
n is the number of seconds between keepalives. 60 seconds is the default. If specified with the x25 route x121-address interface command, this option controls the keepalive behavior of TCP received calls. If specified with x25 route x121-address ip command, this option controls the keepalive behavior of calls sent to the TCP. |
| xot-keepalive-tries p | X25-over-TCP (XOT). p specifies the number of times keepalives should be sent before dropping the connection. The default for p is 4.
If specified with the x25 route x121-address interface command, this option controls the behavior of TCP received calls. If specified with x25 route x121-address ip command, this option controls the behavior of calls sent to the TCP. |
| alias type number | Keyword and interface type and the unit or port number of the interface alias. Encapsulation calls are normally accepted when the destination address is that of the interface (or the zero-length X.121 address). Aliases allow the specified interface to accept calls with other destination addresses. |
| substitute-source rewrite-pattern | (Optional) See Table 13-20 and Table 13-21 for summaries of pattern and character matching, respectively. |
| substitute-dest rewrite-pattern | (Optional) Specifies the called X.121 address to replace in locally routed X.25 calls. (For backwards compatibility, the substitute keyword will be accepted as substitute-dest and written to nonvolatile memory in the new format.) The backslash (\) character is treated specially in the argument rewrite-pattern; it indicates that the digit immediately following it selects a portion of the original called address to be inserted in the new called address. The characters \0 are replaced with the entire original address. The characters \1 through \9 are replaced with the strings that matched the first through ninth parenthesized parts of X.121-pattern. See Table 13-22 for a summary of pattern rewrite elements. |
No entry is created in the X.25 routing table.
Global configuration
The X.25 routing table is consulted when an incoming call is received that should be forwarded to its destination. Two fields are used to determine the route: the called X.121 network interface address (or destination host address), and the X.25 packet's Called User Data (CUD) field. When the destination address and the CUD of the incoming packet fit the X.121 and CUD patterns in the routing table, the call is forwarded.
The order in which X.25 routing table entries are specified is significant; the list is scanned for the first match. The optional argument # position (# followed by a number) designates the line number at which to insert the new router. If no position parameter is given, the entry is appended to the end of the routing table.
The argument X.121-address can be either an actual X.121 destination address or a regular expression such as 1111*, representing a group of X.121 addresses.
The optional Call User Data pattern can be specified as a printable ASCII string. Both the X.121 address and Call User Data can be written using UNIX-style, regular expressions. The Call User Data field is matched against any data in the call, which is commonly 4 bytes long.
X.121 address and Call User Data are used to find a matching routing table entry. The list is scanned from the beginning to the end and each entry is pattern-matched with the incoming X.121 address and Call User Data to the X.121 and Call User Data in the routing table entry. If the pattern match for both entries succeeds, then that route is used. If the incoming call does not have any Call User Data, then only the X.121 address pattern match need succeed with an entry that only contains an X.121 pattern. If Call User Data is present, and while scanning, a route is found that matches the X.121 address but does not have a Call User Data pattern, then that route is used when a dual match cannot be found. Regular expressions are used to allow pattern-matching operations on the X.121 addresses and Call User Data. A common operation is to do prefix matching on the X.121 DNIC field and route accordingly. For example, the pattern ^3306 will match all X.121 addresses with a DNIC of 3306. The caret (^) is a special regular expression character that anchors the match at the beginning of the pattern.
If a matching route is found, the incoming call is forwarded to the next hop depending on the routing entry. If no match is found, the call is cleared. If the route specifies a serial interface running X.25, the router will attempt to forward the call over that interface. If the interface is not operational the remaining routes will be checked for forwarding to an operational interface. If the interface is operational but out of available virtual circuits, the call will be cleared. Otherwise, the expected Clear Request or Call Accepted message will be forwarded back toward the originator. The "null 0" interface can be used as the destination to refuse calls to specific locations. A call cannot be forwarded out the interface it arrived on.
If the matching route specifies an IP address, a TCP connection will be established to port 1998 at the specified IP address, which must be another Cisco router. The Call Request packet will be forwarded to the remote router, where it will be processed in a similar fashion. If a routing table entry is not present or the serial interface is down or out of virtual circuits, a Clear Request will be sent back and the TCP connection will be closed. Otherwise, the call will be forwarded over the serial interface and the expected Clear Request or Call Accepted packet will be returned. Incoming calls received via TCP connections that match a routing entry specifying an IP address will be cleared. This restriction prevents Cisco routers from establishing a TCP connection to another router that would establish yet another TCP connection. A router must always connect to the remote router with the destination DTE directly attached.
See Table 13-20, Table 13-21 and Table 13-22 for summaries of pattern matching, character matching, and pattern rewrite elements. A more complete description of the pattern-matching characters is found in the "Regular Expressions" appendix.
Note that address substitution is only performed on routes to an interface. When running X.25 over IP, address substitution can be performed on the destination IP system if the destination system is configured with the appropriate X.25 routing commands.
| Pattern | Description |
|---|---|
| * | Matches 0 or more sequences of the regular expressions. |
| + | Matches 1 or more sequences of the regular expressions. |
| ? | Matches 0 or 1 sequences of the regular expression.1 |
| Character | Description |
|---|---|
| ^ | Matches the beginning of the input string. |
| $ | Matches the end of the input string. |
| \char | Matches the single character char specified. |
| . | Matches any single character. |
| Pattern | Description |
|---|---|
| \0 | Replaces the entire original address. |
| \1...9 | Replaces strings that match the first through ninth parenthesized part of the X.121 address. |
The following example uses regular expression pattern matching characters to match just the initial portion of the complete X.25 address:
x25 route ^3107 interface serial 0
In the following example, if a call comes in on interface serial 0 and matches any X.121-address pattern, the call will be accepted for encapsulating traffic configured for the interface using x25 map commands:
x25 route .* alias serial 0
In the following example, a call will be accepted if destined for either the VAX X.121 address or the address given in the x25 address interface command:
x25 route vax-x121-address alias serial 0
The following example configures alternate IP addresses for the routing entry. In the event the first address listed is not available, the next address is tried, and so on until a connection is made:
x25 route ^3106 ip 131.08.2.5 131.08.7.10 131.08.7.9
To enable X.25 switching or tunneling, use the x25 routing global configuration command. To disable the forwarding of X.25 calls, used the no form of this command.
x25 routing [use-tcp-if-defs]| use-tcp-if-defs | (Optional) May be used to modify the acceptance of calls received over TCP. |
Disabled
Global configuration
The x25 routing command enables local switching and remote switching (also called tunneling which routes X.25 traffic between two routers via a TCP connection). X.25 calls will not be forwarded until this command is issued.
The use-tcp-if-defs keyword may be needed when receiving remotely routed calls from routers using older software versions. Normally calls received over a TCP connection (remote routing reception) will have the flow control parameters (window sizes and maximum packet sizes) indicated, because proper operation of routed X.25 requires that these values match at both ends of the connection.
Some previous versions of our software, however, do not ensure that these values are present in all calls. In this case the router normally forces universally acceptable flow control values (window sizes of 2 and maximum packet sizes of 128) on the connection. Because some equipment disallows modification of the flow control values in the call confirm, the use-tcp-if-defs keyword will cause the router to use the default flow control values of the outgoing interface and indicate the resulting values in the call confirm. This modified behavior may allow easier migration to newer versions of the router code.
The following example enables X.25 switching:
x25 routing
To specify a sequence of packet network carriers, use the x25 rpoa global configuration command. To remove the specified name, use the no form of this command.
x25 rpoa name number| name | Recognized Private Operating Agency (RPOA), which must be unique with respect to all other RPOA names. It is used in the x25 facility and x25 map interface configuration commands. |
| number | A sequence of 1 or more numbers used to describe an RPOA; up to 10 numbers are accepted. |
No packet network carriers are specified.
Global configuration
This command specifies a list of transit RPOAs to use, referenced by name.
The following example sets an RPOA name and then send the list via the X.25 user facilities:
x25 rpoa green_list 23 35 36 interface serial 0 x25 facility rpoa green_list x25 map ip 131.108.170.26 10 rpoa green_list
To omit the destination address in outgoing calls, use the x25 suppress-called-address interface configuration command. To reset this command to the default state, use the no form of this command.
x25 suppress-called-addressThis command has no arguments or keywords.
The called address is sent.
Interface configuration
This command omits the called (destination) X.121 address in Call Request packets and is required for networks that expect only subaddresses in the called address field.
The following example suppresses or omits the called address in Call Request packets:
interface serial 0 x25 suppress-called-address
To omit the source address in outgoing calls, use the x25 suppress-calling-address interface configuration command. To reset this command to the default state, use the no form of this command.
x25 suppress-calling-addressThis command has no arguments or keywords.
The calling address is sent.
Interface configuration
This command omits the calling (source) X.121 address in Call Request packets and is required for networks that expect only subaddresses in the calling address field.
The following example suppresses or omits the calling address in Call Request packets:
interface serial 0 x25 suppress-calling-address
Use the x25 t10 interface configuration command to set the value of the Restart Indication retransmission timer (T10) on DCE devices.
x25 t10 seconds| seconds | Time in seconds. The default is 60 seconds. |
60 seconds
Interface configuration
The following example sets the T10 timer to 30 seconds:
interface serial 0 x25 t10 30
To set the value of the Incoming Call timer (T11) on DCE devices, use the x25 t11 interface configuration command.
x25 t11 seconds| seconds | Time in seconds. The default is 180 seconds. |
180 seconds
Interface configuration
The following example sets the T11 timer to 90 seconds:
interface serial 0 x25 t11 90
To set the value of the Reset Indication retransmission timer (T12) on DCE devices, use the x25 t12 interface configuration command.
x25 t12 seconds| seconds | Time in seconds. The default is 60 seconds. |
60 seconds
Interface configuration
The following example sets the T12 timer to 30 seconds:
interface serial 0 x25 t12 30
To set the value of the Clear Indication retransmission timer (T13) on DCE devices, use the x25 t13 interface configuration command.
x25 t13 seconds| seconds | Time in seconds. The default is 60 seconds. |
60 seconds
Interface configuration
The following example sets the T13 timer to 30 seconds:
interface serial 0 x25 t13 30
To set the value of the Restart Request retransmission timer (T20) on DTE devices, use the x25 t20 interface configuration command.
x25 t20 seconds| seconds | Time in seconds. The default is 180 seconds. |
180 seconds
Interface configuration
The following example sets the T20 timer to 90 seconds:
interface serial 0 x25 t20 90
To set the value of the Call Request timer (T21) on DTE devices, use the x25 t21 interface configuration command.
x25 t21 seconds| seconds | Time in seconds. The default is 200 seconds. |
200 seconds
Interface configuration
The following example sets the T21 timer to 100 seconds:
interface serial 0 x25 t21 100
To set the value of the Reset Request retransmission timer (T22) on DTE devices, use the x25 t22 interface configuration command.
x25 t22 seconds| seconds | Time in seconds. The default is 180 seconds. |
180 seconds
Interface configuration
The following example sets the T22 timer to 90 seconds:
interface serial 0 x25 t22 90
To set the value of the Clear Request retransmission timer (T23) on DTE devices, use the x25 t23 interface configuration command.
x25 t23 seconds| seconds | Time in seconds. The default is 180 seconds. |
180 seconds
Interface configuration
The following example sets the T23 timer to 90 seconds:
interface serial 0 x25 t23 90
To set the data packet acknowledgment threshold, use the x25 th interface configuration command.
x25 th delay-count| delay-count | Value between zero and the input window size. A value of 1 sends one Receiver Ready acknowledgment per packet. The default is 0, which disables the acknowledgment threshold. |
0 (which disables the acknowledgment threshold)
Interface configuration
This command instructs the router to send acknowledgment packets when it is not busy sending other packets, even if the number of input packets has not reached the input window size count.
The router sends an acknowledgment packet when the number of input packets reaches the count you specify, providing there are no other packets to send. For example, if you specify a count of 1, the router will send an acknowledgment per input packet if unable to "piggyback" the acknowledgment of an outgoing data packet. This command improves line responsiveness at the expense of bandwidth.
This command only applies to encapsulated traffic over X.25 (datagram transport), not to routed traffic (local or remote).
The following example sends an explicit Receiver Ready acknowledgment when it has received five data packets that it has not acknowledged:
interface serial 1 x25 th 5
To override the X.121 addresses of outgoing calls forwarded over a specific interface, use the x25 use-source-address interface configuration command. Use the no form of this command to prevent updating the source addresses of outgoing calls.
x25 use-source-addressThis command has no arguments or keywords.
Disabled
Interface configuration
Some X.25 calls, when forwarded by the X.25 switching support, need the calling (source) X.121 address updated to that of the outgoing interface. This is necessary when forwarding calls from private data networks to public data networks.
The following example shows how to prevent updating the source addresses of outgoing X.25 calls on interface serial 0 once calls have been forwarded:
interface serial 0 no x25 use-source-address
To change the default incoming window size to match that of the network, use the x25 win interface configuration command.
x25 win packets| packets | Packet count that can range from 1 to one less than the window modulus. |
2 packets
Interface configuration
This command determines the default number of packets a virtual circuit can receive before sending an X.25 acknowledgment. To maintain high bandwidth utilization, assign this limit the largest number that the network allows.
The following example specifies that five packets may be received before sending an X.25 acknowledgment:
interface serial 1 x25 win 5
To change the default outgoing window size to match that of the network, use the x25 wout interface configuration command.
x25 wout packets| packets | Packet count that can range from 1 to one less than the window modulus. |
2 packets
Interface configuration
This command determines the default number of packets a virtual circuit can send before waiting for an X.25 acknowledgment. To maintain high bandwidth utilization, assign this limit the largest number that the network allows.
The following example specifies a default limit of five for the number of outstanding unacknowledged packets for virtual circuits:
interface serial 1 x25 wout 5
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