Hi Taqdir Someone like Marko is going to be better equipped to answer this question, but I'll throw in my 2p.
Typically with MPLS VPNs, the penultimate (P) router performs the PHP operation and pops the Egress PE label. As such, the Egress PE receives a labelled packet with only a single label, the VPN Label, and, as it is labelled, the Egress PE needs to consult the LFIB (i.e. mpls forwarding table). After consulting the Local Label field of the mpls forwarding table to find a match, the Egress PE sees the outgoing label as No Label (for routes learned from CE), knows both the Outgoing Interface & Next Hop IP, & hence removes label stack and forwards packet as an IP packet. So as you can see, there is no IP lookup here (for routes learned from CE's). Consider the situation whereby the Egress PE has 2 or more interfaces in the same VRF. If only a single VPN label was assigned to multiple routes learned from CE's in the same vrf , the Egress PE would not know which Outgoing Interface & Next Hop to use in order to forward the packet. For local routes on the Egress PE in the vrf, the aggregate label is associated with them, and after a label pop operation, the cef vrf table IS consulted. Hope this helps in some way. Regards Roy @routeleaker On 28 April 2011 05:00, Taqdir Singh <[email protected]> wrote: > Hello Team, > > > As I understand vpn label is used to know which vrf that packet belongs to. > > But if VRF has 1000 of routes...why there would be 1000 of VPN labels ? > > should not there be only one VPN label per VRF for all routes into that VRF > ? > > what is the concept behind this ? what is the benifit of having so many VPN > labes per VRF > > > -- > > > -Taq > _______________________________________________ > 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 > -- Regards Roy _______________________________________________ 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
