[j-nsp] L3VPN PE-CE multihoming with OSPF

[Harry Reynolds]

If I follow, yes, this is supported and where sham links come into play. You can set a metric on the sham that runs over the L3vpn core so as to prefer intra site routing vs use of the backbone. 

The up/down bits in OSPF type 1-3s, or use of route tags for externals prevent looping. Also, in the VRF the BGP versions of the remote ospf sham learned routes remain preferred so still forward to remote site based on BGP version of L3vpn route even though ospf versions are also in the vrf.

HTHs




-----Original Message-----
From: juniper-nsp-bounces at puck.nether.net [mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of Leigh Porter
Sent: Tuesday, November 20, 2012 6:34 AM
To: juniper-nsp at puck.nether.net
Subject: [j-nsp] L3VPN PE-CE multihoming with OSPF

Hey Folks,

I have a somewhat typical duel PE and duel CE scenario. However, the two PE and two CE routers are all in the same subnet and the two PE routers routing instances can see eachother over OSPF.

I'm not sure if this is wise.

Should routing instances belonging to the same MPLS VPN be able to exchange routes over OSPF when OSPF is the PE-CE routing protocol and those OSPF routes will be part of the VPN's routing table and exported with BGP?

Could there then be an issue where a route is learned by PE-A from PE-B with OSPF, then from PE-B to PE-A with BGP and then around and around creating a route that never gets anywhere because it's self sustained?

--
Leigh Porter

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