[c-nsp] BGP next-ASN check built-in ?

[Brian Turnbow]

Hi

See in-line

> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-
> bounces at puck.nether.net] On Behalf Of tim
> Sent: lunedì 11 aprile 2011 11:17
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] BGP next-ASN check built-in ?
> 
> Hi list,
> 
> I thought I had read something about that but cannot find the pointers
> anymore:
> 
> Does the Cisco default-configuration check in BGP inbound announcements,
> if the first ASN of the AS path is the ASN which is configured as
> "neighbor ... remote-as"?

Yes, you can disable it with no bgp-enforce-first-as globally for BGP.




> 
> Example, is the following check built-in the BGP code and therefore not
> needed to configure:
> 
> """
> router bgp 65001
>  neighbor 129.168.1.1 remote as 65002
>  ...
>  neighbor 129.168.1.1 filter-list 1 in
> !
> ip as-path access-list 1 permit ^65002_
> ip as-path access-list 1 deny .*
> """
> 
> If so, at some exchange-points there are route-servers which strip their
> own ASN out of the path.  How would one configure such a setup from the
> client side?

Using the command above will accept the route-server announcements.
Then use your filters to decide what to accept from the route servers.

HTH 

Brian

> 
> Thanks in advance,
> -tim
> --
> tim at haitabu.net
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