send-label and next-hop-unchanged

skanda · ‎02-11-2012

I have two questions and I have find it every hard find the answers.

1. send-label.

When you send-label through BGP for PE loop-backs addresses, it should be in sh mpls forwarding. But it is not, but when do sh mpls forwarding x.x.x.x, it is showing up the BGP label. Unless things are changed on the SR version of the IOS software ?

2. next-hop-unchanged.

When this command suppose to work ? When I use the next-hop-changed between two MP-ebgp neighbors, it is not working. These two neighbors are not route-reflectors in their local AS's. Is it this command support work on the route-reflector PE routers only ?

regards,

Skanda

Nataliya Omelyanyuk · ‎02-13-2012

Hi,

based on your question layout, I suppose you try to configure MPLS inter-AS VPN Option 3 (Multi-Hop MP-eBGP Between RR and eBGP Between ASBRs).

In that case send-label command is configured on ASBR routers to ensure label distribution between AS and create a end-to-end LSP between ingress local PE and egress remote PE.

Next-hop-unchanged for this scenario needed on RR to optimize the path and to avoid a new label imposition as with new next-hop imposed on RR LSP will be broken.

Please find below link described configuration in more details:

http://www.cisco.com/en/US/partner/docs/ios-xml/ios/mp_ias_and_csc/configuration/15-2s/mp-vpn-connect-ipv4.html#GUID-C72BEAB8-2EE0-4CC6-88D4-07D3056A0963

BR,

Nataliya.