BGP Local AS

[Kaushik Ray]

Hello All

When using the local-as command under address-family ipv4 vrf, is the AS local to the specific Router or is it local to whole MPLS infrastructure?

Can anybody advise on this please?

Many Thanks in advance.

[Nagendra Kumar Nainar]

Hi Kaushik,

bgp local-as is per neighbor specific. You can have 2 neighbors on same router one with local-as and other without. By default, each router will include the AS number from "router bgp <as-number>" while sending the OPEN message. With bgp local-AS, you override it and make the router use the configured AS.

This command is useful incase of migration.

HTH,

Nagendra

[Kaushik Ray]

Hi Nagendra

Thanks for your reply; also one more thing I wanted to ask if there are two routers both using the same main AS say 123 and one using local as as 12 and the other using local as using 23 will they still share the routes via the AS 123 and the local would not affect this?

thanks

[Nagendra Kumar Nainar]

In this case, the session will be established as eBGP between AS 12 and 23. local-as will be considered as "My AS" in your OPEN message.

-Nagendra