Question on BGP synchronization

Unanswered Question
Jun 5th, 2009

All,

I have a small topology:

RouterA(AS1) -> RouterB(AS2) -> RouterC(AS2) -> RouterD(AS3)

RouterB learns of networks from RouterA, but it doesn't send these networks to RouterC with synchronization turned on.

If I turn synchronization off, then I get the routes to RouterB. I'm trying to mimic the example at:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800c95bb.shtml#synch

It doesn't seem like it's working correctly though. What I have is the following:

RouterA:

networks 1.1.1.0/24 2.2.2.0/24

RouterB:

networks 3.3.3.0/24

Sees all of RouterA's networks: 1.1.1.0/24 and 2.2.2.0/24

RouterC:

networks 4.4.4.0/24

with sync turned on, it doesn't even get RouterB's 3.3.3.0/24 network. Turn sync off, I get RouterA and RouterB's networks

RouterD:

network 5.5.5.5/32

Thanks,

John

I have this problem too.
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John Blakley Fri, 06/05/2009 - 12:53

Okay, so the problem is fixed. Apparently, because I only have two routers using iBGP, the router knows this and doesn't propagate the route to the "last" router in iBGP.(If anyone can verify this I'd appreciate it.)

I created an eigrp process on RouterB and RouterC, and I redistributed bgp into eigrp on RouterB. RouterC got all of the routes as external eigrp routes, and then RouterD got all of the routes as BGP routes.

John

Jon Marshall Fri, 06/05/2009 - 13:32

John

I was going to explain IGBP synchronisation but a quick check showed this was already covered in one of your other threads. So i'm assuming you are asking something slightly different here ?

Not sure exactly what it is tho :-) Could you perhaps clarify ?

Jon

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