From: Michelle T (mtruman@xxxxxxxxxxxxxxx)
Date: Sun Dec 31 2000 - 14:54:04 GMT-3
If you think about a typical real world scenario, where the IGP is used as
somewhat of a cargo carrier, doing the heavy lifting for BGP edge routers
within the entire corporate wan, then usually, you want the BGP routes to go
away, should the IGP routes fail. The idea being you never want BGP to
blackhole a route to any given destination. Paritcularly if another BGP edge
router could have gotten you there via that ingress point. Of course, in
lab/ccie environments, it seems we are asked to turn all real world rules of
thumb upside down and perform unnatural acts with routing protocols. Having
said that however, I would expect the test designers to test our
understanding of how BGP and IGP's interact and set up a scenario so that
internal destinations are reachable via other BGP ingress to a network when
a particular internal path fails.
Michelle
----- Original Message -----
From: "Connary, Julie Ann" <jconnary@cisco.com>
To: <ccielab@groupstudy.com>
Sent: Sunday, December 31, 2000 9:58 AM
Subject: network statement in bgp - best practice question
> Hi All,
>
> I'm working on some labs and I am doing this one lab using first
> redistribution and second
> network statements under bgp.
>
> My question is if you have 3 ibgp neighbors in AS 200. Router 1 is EBGP
> peered to AS100. Router 2 and
> 3 are EBGP peered to AS300. Since Router 1, 2 and 3 are in the same AS,
> running an IGP, so they
> have knowledge of all internal routes, is it best to put a network
> statement for the local network numbers in
> all 3 BGP routers or just one?
>
> I am using network 10.x.x.x, so I put in router 2 network statements for
> all the particular
> subnets and then an aggregate-summary address (I guess, I could just have
> left auto-summary on also).
> I noticed that routers 1 and 3 get
> the route via IBGP, since they have routes to the 10.x.x.x network it
> becomes a best route
> and they advertise it via EBGP.
>
> Any rules of thumb? Perhaps it is best to put it in all border routers
> incase internal routing fails?
>
> Julie Ann
> ------------------------------------------------------------------------
> Julie Ann Connary
> | | Network Consulting Engineer
> ||| ||| Federal Support Program
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>
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>
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