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9.7 Autonomous System

AS (Autonomous System) is one of the essential element of BGP. BGP is a distance vector routing protocol. AS framework provides distance vector metric and loop detection to BGP. RFC1930 - Guidelines for creation, selection, and registration of an Autonomous System (AS) describes how to use AS.

AS number is tow octet digita value. So the value range is from 1 to 65535. AS numbers 64512 through 65535 are defined as private AS numbers. Private AS numbers must not to be advertised in the global Internet.