Synchronisation Problem

[srowles]

I am having some problems getting a BGP route synchronised.

Here is my BGP table:

* i215.15.1.0 100.251.100.254 0100 0 1099 i

THE IGP ROUTE IS IN THE ROUTING TABLE AS FOLLOWS

O E1 215.15.1.0/24 [110/114] via 200.1.1.9, 1:13:37,

AS IS THE ROUTE TO THE NEXT HOP

O E1 100.0.0.0/8 [110/114] via 200.1.1.9

HOWEVER WHEN I PERFORM A SHOW IP BGP 215.15.1.0 THE ROUTE IS SHOWN AS NOT SYNCHRONISED AND CONSEQUENTLY DOES NOT GET ADVERTISED OUT OF MY AS. CAN ANYONE POINT OUT WHAT I MIGHT BE DOING WRONG TAKING INTO CONSIDERATION THAT I DO NOT WANT TO TURN OFF SYNCHRONISATION.

[mhussein]

Check the output of "sho ip route 215.15.1.0 255.255.255.0" and "sho ip bgp 215.15.1.0 255.255.255.0".

The route should be synchronised as long as it is learned via IGP. So if you run the above "show" commands, make sure that the subnet mask matches in both the BGP and IGP routing tables.

Regards,

Mustafa Hussein

Comark, Inc.

[srowles]

Thanks for the advice. I think I've sussed it. The IGP update is coming from an OSPF neighbor that is not the same router that originated the BGP route. Aparrently the router ID of the BGP neighbor and the OSPF router that is advertising the LSA must be the same for the route to be synchronised. This is apparently only an issue when using OSPF. This seems to be the case as I forced the BGP neighbor to have the same router-id as the OSPF neighbor (for testing purposes) and the route then displayed as synchronised.

Steve

[mhussein]

This goes into the bag of tricks!

Thanks for sharing ...

Mustafa