Table of Contents
Advertisement
router bgp
format, use the bgp asnotation dot command under router configuration mode. When the asdot format
is enabled as the default, any regular expressions to match 4-byte autonomous system numbers must be
written using the asdot format, or the regular expression match will fail.
although you can configure 4-byte autonomous system numbers in either asplain or asdot format, only
one format is used to display show command output and control 4-byte autonomous system number
matching for regular expressions, and the default is asplain format. To display 4-byte autonomous system
numbers in show command output and to control matching for regular expressions in the asdot format,
you must configure the bgp asnotation dot command. After enabling the bgp asnotation dot command,
a hard reset must be initiated for all BGP sessions by entering the clear ip bgp * command.
Note
If you are upgrading to an image that supports 4-byte autonomous system numbers, you can still use
2-byte autonomous system numbers. The show command output and regular expression match are not
changed and remain in asplain (decimal value) format for 2-byte autonomous system numbers regardless
of the format configured for 4-byte autonomous system numbers.
Table 8
Format
asplain
asdot
Table 9
Format
asplain
asdot
Reserved and Private Autonomous System Numbers
In Cisco IOS Release 12.0(32)S12, 12.0(32)SY8, 12.2(33)SXI1, 12.4(24)T, Cisco IOS XE Release 2.3
and later releases, the Cisco implementation of BGP supports RFC 4893. RFC 4893 was developed to
allow BGP to support a gradual transition from 2-byte autonomous system numbers to 4-byte
autonomous system numbers.
Note
A new reserved (private) autonomous system number, 23456, was created by RFC 4893 and this number
cannot be configured as an autonomous system number in the Cisco IOS CLI.
RFC 5398, Autonomous System (AS) Number Reservation for Documentation Use, describes new
reserved autonomous system numbers for documentation purposes. Use of the reserved numbers allow
configuration examples to be accurately documented and avoids conflict with production networks if
these configurations are literally copied. The reserved numbers are documented in the IANA
Cisco MWR 2941 Router Command Reference, Release 15.0(1)MR
382
Default Asplain 4-Byte Autonomous System Number Format
Configuration Format
2-byte: 1 to 65535
4-byte: 65536 to 4294967295
2-byte: 1 to 65535
4-byte: 1.0 to 65535.65535
Asdot 4-Byte Autonomous System Number Format
Configuration Format
2-byte: 1 to 65535
4-byte: 65536 to 4294967295
2-byte: 1 to 65535
4-byte: 1.0 to 65535.65535
Cisco MWR 2941 Router Command Reference, Release 15.0(1)MR
Table 8
Show Command Output and Regular Expression
Match Format
2-byte: 1 to 65535
4-byte: 65536 to 4294967295
2-byte: 1 to 65535
4-byte: 65536 to 4294967295
Show Command Output and Regular Expression
Match Format
2-byte: 1 to 65535
4-byte: 1.0 to 65535.65535
2-byte: 1 to 65535
4-byte: 1.0 to 65535.65535
and
Table 9
show that
OL-23890-01
Advertisement
Table of Contents
