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iBGP Redistribution issue

cdegroat82
Level 1
Level 1

Hi - Im currently running a GNS3 lab with 4 3640 routers.  I am running OSPF & BGP, OSPF to redistribute my connected subnets - and BGP to redistribute my static subnets.  3 out of the 4 seem to be working properly.  Core #1, 2 and 4 are receiving the proper static routes including the gateway of last resort.  However core #3, is only getting routes from Core #4 for some reason.  All BGP sessions are up and established.  Not really sure why its not working.

I attached the BGP configs and routing table outputs below.  Is there something Im missing?

2 Replies 2

cadet alain
VIP Alumni
VIP Alumni

Hi,

you haven't got a full mesh and iBGP won't advertise an iBGP learned route to another iBGP neighbour so routes learned from 1 and advertised to 2  and 4 won't get to 3.

you can see it when looking at the advertised routes  on Core 2 towards Core 3 for example with the following command:

sh bgp ipv4 unicast neighbour X.X.X.X advertised

Now it should receive prefixes of Core 2 and Core 4 but it would be easier to see what's happening with a diagramm and full configs from the routers.

Regards

Alain

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Ill take a screen shot of the diagram in a bit.  As for the full mesh that was the end goal - but I ran in to this issue first.  I ran sh bgp ipv4 unicast neighbour X.X.X.X advertised and see Core 1 advertising correctly to 2 and 4.  Doing some more reading - I see why Im having the issue, which is more or less the design of iBGP.

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