peer-as (Protocols BGP)
Syntax
peer-as autonomous-system;
Hierarchy Level
[edit logical-systems logical-system-name protocols bgp], [edit logical-systems logical-system-name protocols bgp group group-name], [edit logical-systems logical-system-name protocols bgp group group-name neighbor address], [edit logical-systems logical-system-name routing-instances routing-instance-name protocols bgp], [edit logical-systems logical-system-name routing-instances routing-instance-name protocols bgp group group-name], [edit logical-systems logical-system-name routing-instances routing-instance-name protocols bgp group group-name neighbor address], [edit protocols bgp], [edit protocols bgp group group-name], [edit protocols bgp group group-name neighbor address], [edit routing-instances routing-instance-name protocols bgp], [edit routing-instances routing-instance-name protocols bgp group group-name], [edit routing-instances routing-instance-name protocols bgp group group-name neighbor address]
Description
Specify the neighbor (peer) autonomous system (AS) number.
For EBGP, the peer is in another AS, so the AS number you specify
in the peer-as statement must be different from the local
router’s AS number, which you specify in the autonomous-system statement. For IBGP, the peer is in the same AS, so the two AS numbers
that you specify in the autonomous-system and peer-as statements must be the same.
The AS numeric range in plain-number format has been extended in Junos OS Release 9.1 to provide BGP support for 4-byte AS numbers, as defined in RFC 4893, BGP Support for Four-octet AS Number Space. RFC 4893 introduces two new optional transitive BGP attributes, AS4_PATH and AS4_AGGREGATOR. These new attributes are used to propagate 4-byte AS path information across BGP speakers that do not support 4-byte AS numbers. RFC 4893 also introduces a reserved, well-known, 2-byte AS number, AS 23456. This reserved AS number is called AS_TRANS in RFC 4893. All releases of the Junos OS support 2-byte AS numbers.
In Junos OS Release 9.2 and later, you can also configure a 4-byte AS number using the AS-dot notation format of two integer values joined by a period: <16-bit high-order value in decimal>.<16-bit low-order value in decimal>. For example, the 4-byte AS number of 65,546 in plain-number format is represented as 1.10 in the AS-dot notation format.
With the introduction of 4-byte AS numbers, you might have a combination of routers that support 4-byte AS numbers and 2-byte AS numbers. For more information about what happens when establishing BGP peer relationships between 4-byte and 2-byte capable routers, see the following topics:
Using 4-Byte Autonomous System Numbers in BGP Networks Technology Overview.
Options
autonomous-system—AS number.
Range: 1 through 4,294,967,295 (232 – 1) in plain-number format for 4-byte AS numbers
Range: 1 through 65,535 in plain-number format for 2-byte AS numbers (this is a subset of the 4-byte range)
Range: 0.0 through 65535.65535 in AS-dot notation format for 4-byte AS numbers
Required Privilege Level
routing—To view this statement in the configuration.
routing-control—To add this statement to the configuration.
Release Information
Statement introduced before Junos OS Release 7.4.