From: Peter van Oene (pvo@usermail.com)
Date: Mon Oct 21 2002 - 19:44:28 GMT-3
This is covered very extensively in the archives. I have actually posted a
few longish responses on the subject myself. The answer surrounds the fact
that route reflection and synchronization are not meant to be used
together, and particularly when using OSPF for an IGP will not function.
At 12:15 AM 10/22/2002 +0200, you wrote:
>Hi,
>
>scenario:
>
> \ /
> AS2010 \ / AS2001
>R7-----------------------R2-----------------R1-----------------R3
> / \
> / \
>
>IGP:
>
>- between R7 and R2 IGP is RIP v2
>- R2,R1 & R3 running OSPF
>- routes fron RIP redistributed in OSPF and v/v
>- full connectivity is established (every router can reach each network in
>bot ASs via its IGP)
>
>BGP:
>
>- EBGP between R7 & R2, IBGP R2,R1 & R3 (partial mesh: R2-->R1--->R3)
>- R1 is Route-Reflector for R2 & R3
>
>
>Problem:
>
>- routes learned via bgp on R1 are marked as valid and best (*>) but same
>routes when reflected to R3 are although marked as valid but not best.
>Detailed view of a prefix learned via R1 shows that prefixes are not
>synched for some reason (enabling "no synch" command proves that). IGP
>Routes in both router's routing table are same.
>
>So now the 1 Mio. $ Question: What is causing BGP prefixes on R3 no to be
>synchronized, despite having routes in routing table toward nexthop and
>same prefixes learned via IGP.
>
>As far I understood the "Synch rule" was that it states that, prfixes
>learned via IBGP should be present in routing table learned via an IGP to
>avoid blackholing traffic and mark prefixes as best to propogate them
>further. is that right?
>
>regards
>
>Azhar M.
>
>PS: configs are available OD.
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