Is there a cisco-equivalent of "loop n"(JunOS) as applicable to local-as

[Randy]

Thanks Oli.




----- Original Message -----
From: Oliver Boehmer (oboehmer) <oboehmer at cisco.com>
To: Randy <randy_94108 at yahoo.com>
Cc: Cisco Network Service Providers <cisco-nsp at puck.nether.net>
Sent: Sunday, March 5, 2017 12:46 AM
Subject: Re: Is there a cisco-equivalent of "loop n"(JunOS) as applicable to local-as

Randy,

>    JunOs "no-prepend-global-as" is the Cisco equivalent of replace-as
>    JunOS "private" is the Cisco equivalent of no-prepend
>    JunOS  "alias" is the Cisco equivalent of Dual-AS
>    JunOS "loop n"; Cisco equivalent ???

I think neighbor foo allowas-in <number> is the cmd you’re looking for..

>    My google-fu is failing me here.
>
>    Example:
>
>    RTR1 and RTR2 in AS64512 are iBGP peers and peer with RTR3 @ AS64514 using local-as 64513
>
>    In the absence of no-prepend in local-as config on RTR1 and RTR2, updates from RTR3 to RTR1 and 2 would have AS 64513 prepended to updates from R3.
>    R2 and R1 would receive ibgp updates from each other with AS64513(local-as) in the as_path - How would the Cisco-RTR1&2 handle these ibgp-updates from each other?

well, IOS/IOS-XR only apply the incoming as-path loop check on eBGP updates, so iBGP updates with your own AS would pass this check just fine, as long as RTR3’s make it into your AS (with the help of allowas-in they would, I guess).


>
>    On JunOS the "loop n" in conjunction with local-as allows me to customize what I accept as applicable to local-as in received updates. Loop 1 would hide ibgp updates received with local-as in as-path; loop 2 would allow upto 1 local-as in as-path.

Not entirely sure which policy you want to achieve, but the above might give you some tools? 

    oli