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Hi Victor,
In general, an OSPF speaking PE router will do two checks for the received routes:
- check the down bits on the received summary LSAs - if it’s set it’ll drop it and won’t advertise it further. - check the domain tag on received external LSA and if they match with the locally configured will be dropped.
Both checks above are for loop preventing purposes.
Now, as soon as you configure a CE router for VRF-lite with OSPF on the upstream (facing the MPLS network and provider PE), the router can be considered as PE router as it starts performing the above two checks. That’s why you need to disable the checks with this command in order to propagate the routes further down, through the VRF-lite CE router.
Regards, Rado
Victor Cappuccio wrote: > Hi People. > > > I am trying to understand vrf capabilities under ospf, please use the > following link as the example for my question > http://tinyurl.com/create.php > > I understand the creation of the tunnels towards each PE using the ssm > address as the destination address in the MDT Tunnel, and that the > source would be the configuration that we do under the VPNv4 BGP > Address family for this auto magical multcast tunnel > > My question is more related to the Routing Context, not to Multicast > (for now ) > what would happen if I configure no capabilities vrf-lite under each > CE? assuming that the routers are configured with ospf instead of RIP > as the routing context > > > is this no capability vrf-lite configuration necessary if ospf was > used as the routing context between the CE/PEs in the CE Router for > that figure? > > I understand that the PE would would ignore the routes that have the > Down Bit set, and this would originate that the route is not > redistributed into MPBGP,, and that this OSPF DB gets marked when they > cross from their area, converting them as Lsa type 3 in other PE, and > with that mark other PE connected to the same site would ignore the > route an solve the possible loops that can be created.. (so this is > the basics) > > but I am stuck with that capability vr-lite under the ospf that runs > between the PE and the CEs, when do we need to configure this? > > Can someone please elaborate more about this? > > Thanks for any comments