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Silver

RR is receiving two updates for single RD

hi all

we are running two RR for mpls vpn routes. As we know RR are prevalent to accept the same route with same rd from different PEs. But in our cloud we are receiving the routes of one RD from different PE which should not be. We are not able to find what the hell with the RR. It gets disappear when we run the show ip bgp neighbor * soft in on PE.

Regards

shivlu jain

5 REPLIES
Silver

Re: RR is receiving two updates for single RD

We are facing the problem from the last few days. At last I made the document which explicity tells about the problem.

I would like to request to experts kindly have a look to problem and if possible provide the solution.

http://shivlu.blogspot.com/2009/01/problem-of-routes-flushing-in-core-of.html

regards

shivlu jain

Hall of Fame Super Silver

Re: RR is receiving two updates for single RD

Hello Shivlu,

I've given a quick look to the link to your blog.

By having two iBGP sessions with both RRs would be correct that PE1 receives one copy of vpnv4 advertisement about remote VRF site.

Each RRS performs its own best path selection and propagates the best path to all other RR clients.

The two RRS share the same cluster-id 0.0.255.220 so they don't exchange routes between them recognizing they are serving the same set of clients.

Then on PE1 the path via RR2 is chosen for its lower IGP metric to BGP next hop (47 for path from RR2, 48 for path via RR1).

This part is standard.

What is strange in your case is the presence of a VRF without any valid ip address associated to it that takes part in the VRF routing table.

This is the element of disturb I think.

so clearly one path is a fake path via PE2 that has no real connection to CE that is indeed connected to PE3.

Hope to help

Giuseppe

Silver

Re: RR is receiving two updates for single RD

thanks Giuseppe . Actually I am looking for why the fake path is coming. Still I am not able to find any relevant ios which can releif me from this.

regards

shivlu jain

Hall of Fame Super Silver

Re: RR is receiving two updates for single RD

Hello Shivlu,

is the VRF defined on PE2 using multiple RTs for import and export ?

I wonder if there is a chance that it is learning the prefix with a RT value and exporting it with another RT value like in a Hub and Spoke or Central Site VPN.

I agree that it shouldn't do it when no valid connected interface in VRF is present.

For example I've seen that if you try to perform ping in VRF for a VRF without any connected interface IOS complains that no valid source address for the ping exists.

Hope to help

Giuseppe

Silver

Re: RR is receiving two updates for single RD

hi Giuseppe

No vrf is defined on PE2. The rts are only used for specific vrf only and vrf is present on only PE3.

regards

shivlu jain

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