Configuring 4-Byte Autonomous System Numbers

This section describes how to configure a 4-byte AS number and how to verify if the BGP peer supports 4-byte AS numbers.

The AS number can be specified in plain number format or in AS-dot notation format on routers running Junos OS Release 9.2 and later. For example, the 4-byte AS number of 65,546 is represented in plain-number format as 65546. The same AS number is represented in AS-dot notation format as 1.10 on routers running Junos OS Release 9.2 and later.

To configure a 4-byte AS number in AS-dot notation format, include the autonomous-system statement and specify the 4-byte AS number. In the following example the AS number is set to 1.10.
user@host# set routing-options autonomous-system 1.10
To configure a 4-byte AS number in plain number format, include the autonomous-system statement and specify the 4-byte AS number. In the following example the AS number is set to 65546.
user@host# set routing-options autonomous-system 65546
After a BGP peer session has been negotiated, you can verify whether the peer supports 4-byte AS numbers or not. To verify whether the peer supports 4-byte AS numbers or not, use the show bgp neighbor command. In the following example the peer does not support 4-byte AS numbers.
user@host# show bgp neighbor 192.168.1.9 | match "AS"
```
Peer: 192.168.1.9+179 AS 65056 Local: 192.168.1.3+52616 AS 65000
  Peer does not support 4 byte AS extension
```

In the following example the peer does support 4-byte AS numbers.

user@host# show bgp neighbor 192.168.1.9
| match "AS"

Peer: 192.168.1.10+52679 AS 1000000000 Local: 192.168.1.3+179 AS 65000
  Peer supports 4 byte AS extension (peer-as 1000000000)

Configuring 4-Byte Autonomous System Numbers

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