I think I found the answer: On the PE, only routes from the routing table are redistributed from BGP into OSPF. Since the OSP routes learned across the back-door link, and advertised to the PE, have a lower AD, they get put in the routing table. The routes learned across the L3VPN are not put in the routing table, and therefor do not get re-distributed into OSPF.
However, I thought the whole purpose of a sham link was so that the customer routers would see the routes learned across the L3VPN as intra-area routes instead of inter-area routes, so you could adjust cost to prefer one over the other. >From what I am seeing in this topology, without the sham link, the customer routers never even see the routes coming from the L3VPN. The end result is the same. Once the sham-link is up, you can tweak cost to route traffic as you want. So I'm probably splitting hairs at this point... But I'm afraid I'm misunderstanding something that will come back and bite me later. Doug -------- Original Message -------- Subject: Re: [OSL | CCIE_RS] OSPF behavior with MPLS VPN, backdoor link, no sham link From: Michael Davis - Webquor <[email protected]> Date: Thu, November 15, 2012 6:18 am To: "[email protected]" <[email protected]> Cc: IPexpert Online Study List <[email protected]> Hi There - I just built a similar config to you and found the same behaviour. No type 3 LSA in the database on the CE from the PE until I shut down the backdoor link. I am using 12.4(15)t on GNS 3. When I build the sham link everything works ok, but why no type 3 before that? Interesting question. Sent from my iPhone On 15/11/2012, at 12:13 PM, "[email protected]" <[email protected]> wrote: > I'm working on a sham link lab, and came across some behavior I don't > understand. I've got the MPLS L3VPN built, and routes are being learned > across it properly. Everything is in area 0, and I've used the same > process ID for the vrf on both PE's. I do not have the sham link > configured yet, so all traffic is going over the back-door link. > > The thing I don't understand is that there are no Type3 LSA's anywhere, > not on the CE routers, nor on the PE vrf's. I only see type 1 and Type 2 > LSA's. If I shut down the back-door link, the Type 3's show up, along > with the O IA routes as expected. > > I would think that while the back-door is up, we would see the Type 2 > LSA's coming across the back-door link, as well as the Type 3 LSA's > being redistributed from MP-BGP. > > What am I missing? > > Thanks, > > Doug > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com > > Are you a CCNP or CCIE and looking for a job? Check out > www.PlatinumPlacement.com > > http://onlinestudylist.com/mailman/listinfo/ccie_rs _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com http://onlinestudylist.com/mailman/listinfo/ccie_rs
