From: Chris Lewis (chrlewiscsco@gmail.com)
Date: Wed Jan 04 2006 - 17:45:32 GMT-3
Michael,
I'd suggest clarifying in your mind one other aspect of these commands, and
that is when the local-as appears or does not appear in the path shown in
the BGP table.
If you add a third router, so your topology is something like this
R1---R2---R3
and have each one advertize a local loopback in to BGP, you should feel
comfortable knowing when each configuration of neighbor local-as, neighbor
local-as no-prepend, and BGP confederations willl make AS 100 either appear
or not appear in neighboring routers BGP tables.
It is quite possible the exam would give you some conditions in terms of
connectivity that would require or forbid confederations, then give you a
BGP table output to replicate that would require you to know how to
configure things to control whether AS 100 does or does not appear in BGP
tables.
Chris
Chris
On 12/30/05, Michael Brooks <michaeljbrooks@gmail.com> wrote:
>
> I need some clarification in regards to a router in a BGP confederation
> forming an ebgp peering relationship.
>
> R1 (AS: 100/Confed AS 65026) <----> ISP-R2 (AS 200)
>
> On R1 would you configure:
>
> R1:
> router bgp 65026
> neighbor 1.1.1.2 remote-as 200 (isp)
> *bgp confederation identifier 100*
>
> ***OR****
>
> R1:
> router bgp 65026
> neighbor 1.1.1.2 remote-as 200 (isp)
> *neighbor 1.1.1.2 local-as 100
> *
> **********************
>
> Both configurations appear to work, but I am curious to know what the
> preferred method is and why ? Also, I noticed the "local-as" command takes
> precedence over the "confederation identifier" command when both
> configured
> at the same time. Are these commands basically inter-changeable when
> configuring ebgp peering relationships (besides the identification of the
> neighbor with local-as command). Your input would be greatly aprreciated.
>
> Thanks,
> Mike
>
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