Solved: BGP AS numbers

wgranada1 · ‎08-12-2008

I have a quick question here would there be a problem if I assign BGP AS number 65145 on a router that already has another AS number? The 65145 I just made up which is perfectly ok right? Sorry someone has always given me a ASN this it the first time I'm making one up.

lamav · ‎08-12-2008

You can only run one instance of BGP on any given router.

The private AS number space is 64512 to 65535. So, in terms of selecting an AS, you're fine. In terms of configuring a second BGP AS on the router, you're not fine.

HTH

Victor

View solution in original post

lamav · ‎08-12-2008

You can only run one instance of BGP on any given router.

The private AS number space is 64512 to 65535. So, in terms of selecting an AS, you're fine. In terms of configuring a second BGP AS on the router, you're not fine.

HTH

Victor

wgranada1 · ‎08-12-2008

Thanks Victor for the info!!!!!

Giuseppe Larosa · ‎08-12-2008

Hello Warren,

a router can be in only one AS number.

You will get an error if try to enter router bgp 65145.

A router can pretend to be in AS 65145 for a specific BGP neighbor by using the local-as option.

neighbor local-as

To customize the AS_PATH attribute for routes received from an external Border Gateway Protocol (eBGP) neighbor, use the neighbor local-as command in address family or router configuration mode. To disable AS_PATH attribute customization, use the no form of this command.

neighbor {ip-address | peer-group-name} local-as [autonomous-system-number [no-prepend [replace-as [dual-as]]]]

no neighbor {ip-address | peer-group-name} local-as

see

http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_bgp3.html#wp1014448

In your case evaluate if you want to put your router in AS 65145 you first need to remove the current BGP process otherwise use the local-option

Hope to help

Giuseppe

wgranada1 · ‎08-12-2008

Is this pretty easy to do? From a quick look at the link you provided it appears so. I'll give it a shot and see how it goes.