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Cisco MWR 2941 Router Command Reference, Release 15.0(1)MR
Release
12.2(33)MRA
15.0(1)MR
Usage Guidelines
This command allows you to set up a distributed routing core that automatically guarantees the loop-free
exchange of routing information between autonomous systems.
Prior to January 2009, BGP autonomous system numbers that were allocated to companies were 2-octet
numbers in the range from 1 to 65535 as described in RFC 4271, A Border Gateway Protocol 4 (BGP-4).
Due to increased demand for autonomous system numbers, the Internet Assigned Number Authority
(IANA) will start in January 2009 to allocate four-octet autonomous system numbers in the range from
65536 to 4294967295. RFC 5396, Textual Representation of Autonomous System (AS) Numbers,
documents three methods of representing autonomous system numbers. Cisco has implemented the
following two methods:
•
•
For details about the third method of representing autonomous system numbers, see RFC 5396.
Asdot Only Autonomous System Number Formatting
In Cisco IOS Release 12.0(32)S12, 12.4(24)T, Cisco IOS XE Release 2.3, and later releases, the 4-octet
(4-byte) autonomous system numbers are entered and displayed only in asdot notation, for example, 1.10
or 45000.64000. When using regular expressions to match 4-byte autonomous system numbers the asdot
format includes a period which is a special character in regular expressions. A backslash must be entered
before the period for example, 1\.14, to ensure the regular expression match does not fail.
the format in which 2-byte and 4-byte autonomous system numbers are configured, matched in regular
expressions, and displayed in show command output in Cisco IOS images where only asdot formatting
is available.
Table 7
Format
asdot
Asplain as Default Autonomous System Number Formatting
In Cisco IOS Release 12.0(32)SY8, 12.2(33)SXI1, 12.0(33)S3, Cisco IOS XE Release 2.4, and later
releases, the Cisco implementation of 4-byte autonomous system numbers uses asplain as the default
display format for autonomous system numbers, but you can configure 4-byte autonomous system
numbers in both the asplain and asdot format. In addition, the default format for matching 4-byte
autonomous system numbers in regular expressions is asplain, so you must ensure that any regular
expressions to match 4-byte autonomous system numbers are written in the asplain format. If you want
to change the default show command output to display 4-byte autonomous system numbers in the asdot
OL-23890-01
Modification
This command was integrated into Cisco IOS Release 12.2(33)MRA.
This command was integrated into Cisco IOS Release 15.0(1)MR.
Asplain—Decimal value notation where both 2-byte and 4-byte autonomous system numbers are
represented by their decimal value. For example, 65526 is a 2-byte autonomous system number and
234567 is a 4-byte autonomous system number.
Asdot—Autonomous system dot notation where 2-byte autonomous system numbers are
represented by their decimal value and 4-byte autonomous system numbers are represented by a dot
notation. For example, 65526 is a 2-byte autonomous system number and 1.169031 is a 4-byte
autonomous system number (this is dot notation for the 234567 decimal number).
Asdot Only 4-Byte Autonomous System Number Format
Configuration Format
2-byte: 1 to 65535
4-byte: 1.0 to 65535.65535
Show Command Output and Regular Expression
Match Format
2-byte: 1 to 65535
4-byte: 1.0 to 65535.65535
Cisco MWR 2941 Router Command Reference, Release 15.0(1)MR
router bgp
Table 7
shows
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