Hi,
I’m trying to repeat the “Interprovider VPN example - Multihop MP-EBGP with P Routers”, using Olive, described at the following link http://www.juniper.net/techpubs/software/junos/junos95/swconfig-vpns/id-11993771.html#id-11976247, where instead of using RSVP-TE to setup LSPs, I want to use LDP. Besides, I cut the links between routers B and C and D and E.
Unfortunately my experiment fails in one point and I do not understand the reason. Control plane seems to work well, VRF are correctly populated, label exchanges are OK. The problem is on data plane.
I followed step by step a packet from CE F to CE A. The problem shows up when the packet reaches router C. Before reaching router C the packet has (correctly) two labels:
- the top one advertised by router PE C to router PE D through BGP (“family inet labeled-unicast” has been used) and associated to the BGP Next-hop, which is the lo0.0 interface of router B,
- the bottom one is the label advertised by router B through the MP-eBGP session between the two PEs B and F.
Now, router C has also the LDP label associated to the lo0.0 interface of router B (the BGP Next-Hop) since the lo0.0 interface of router B is advertised by OSPF and there is an OSPF path toward this interface. Also, LDP is configured on all backbone routers (PE and P).
Now, my intuition says that router C should swap the top label above to the LDP label. Should it happen, the packet would go straight to PE B, and arrive at router B with only the VPN label. Unfortunately router C instead of label swapping does a label popping, thus sending packet to router G with only the VPN label. And of course router G drops the packet. In other words, continuity of LSP from PE E to BGP Next-Hop (lo.0 of PE B), breaks at router C
Any idea of the reason why does this happen ? It seems as there is no connection between LDP label associated to BGP Next-Hop, advertised by G to router C through LDP and the label advertised by router C to router D through BGP.
Topology is on Juniper document, configurations in the attached file (I only changed IP addresses).
Thanks a lot in advance to anyone can help me.