Re: BGP and AS loop prevention

Nate,

Do you think there is a reason that the AS100 will not accept another
AS100 sending it prefixes? Think about for a moment. What does a BGP
Speaker do with prefixes if it thinks they came from somewhere else?
Now ask yourself can you change this behavior and if you can then how
will you do it?

On Mon, Oct 19, 2009 at 11:12 PM, Nate Lee <natetlee_at_gmail.com> wrote:
> I have a scenario labbed up where I have an discontiguous BGP AS split by
> another AS, something like this: (AS100) <> (AS 200) <> (AS 100).
>
> I am trying to get the prefixes on the AS 100 routers to show up in each
> others BGP tables. I have implemented the neighbor x.x.x.x allowas-in
> command on the AS 100 routers on their neighbor statements facing the AS 200
> routers but it does not seem to work. When I do a SHOW IP BGP NEIGH x.x.x.x
> ADVERTISED-ROUTES on the AS 200 routers, I see that the AS 200 router will
> not send the route that originated in the far side AS 100.
>
> Is there some sort of configuration needed on the AS 200 routers to allow
> them to send a route with an AS PATH that contains the AS they are sending
> into? I was under the impression that they do not perform an outgoing AS
> PATH check.
>
> Thanks!
>
> Nate
>
>
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Received on Mon Oct 19 2009 - 23:46:45 ART