The explanations by Joe and Marcel are very good. As you are planning to lab and debug this, here's a free IPexpert lab task :-)
You have a CE that is running OSPF in a VRF (VRF-lite) that is connected to a PE which is redistributing routes from MP-BGP into OSPF. Now ensure that these routes get in the routing table of the CE without using the 'capability vrf-lite' command! -- Regards, Rick Mur CCIE2 #21946 (R&S / Service Provider) Sr. Support Engineer – IPexpert, Inc. URL: http://www.IPexpert.com On 15 mei 2010, at 14:01, Marcel Lammerse wrote: > Hi Rob, > > it is used in an mpls-based vpn scenario, where the ce speaks ospf with the > pe. In order to enable routing to remote vpn sites, the pe has to > redistribute mbgp prefixes into ospf with the DN-bit set. The DN-bit is used > as a loop prevention mechanism, because if an ospf update with the DN-bit set > would somehow reach the pe, it should not accept the update into the vrf > again. > > However, let's say you have vrf lite with ospf to the pe configured on the > ce, this becomes a problem. Because the ce will not import any routes that > have the DN-bit set into the vrf and you would not be able to route to the > remote vpn sites. By configuring the capability vrf-lite command, the > filtering rule is relaxed and the pe routes will be imported into the vrf on > the ce. > > Therefore, to answer your question, you would see the DN-bit set on lsas > received from a pe that redistributes mbgp routes into ospf. > > HTH > Marcel > > On 14/05/2010, at 11:04 , Robert Simmons wrote: > >> All, >> >> Can anyone shoot me a quick scenario where I would need to use the >> capability vrf-lite command? I need something where I can actually look at >> debugs and in the ospf database to see the DN bit checked? >> >> Thanks >> >> -Rob >> >> >> _______________________________________________ >> For more information regarding industry leading CCIE Lab training, please >> visit www.ipexpert.com > > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com
