Question on BGP synchronization

John Blakley · ‎06-05-2009

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

HTH, John *** Please rate all useful posts ***

John Blakley · ‎06-05-2009

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

HTH, John *** Please rate all useful posts ***

Jon Marshall · ‎06-05-2009

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