MPLS LDP (Label Distribution Protocol)

Hi Rene,

Thanks for a great explanation

Quick question if you do not mind… the prefixes that will be installed on the LFIB, do they need to be learned by the same routing protocol?

I set up the following lab in order to fully understand how it works (I came across a similar setup during one of my mock labs):

Cust1A <-> ISP11 <-> R1 <-> R2 <-> ISP21 <-> Cust1B

  • R1 and R2 are running OSPF and MPLS is enabled (they should be the transport network)
  • ISP11 and ISP21 are running eBGP with R1 and R2 respectively and MP-eBGP between themselves to exchange VPNv4 prefixes
  • VRF Cust1 on ISP11 peers with Cust1A using EIGRP, and the same goes for VRF Cust1 on ISP12 with Cust1b
MPLS labels are exchanged between ISP11 and R1, but they are not installed on the LFIB ("show mpls forwarding-table" on R1 shows "no label" for any destination reachable via ISP11.

If ISP11, R1, R2 and ISP12 run a common protocol (let’s say all of them are in OSPF area 0), everything works fine.

I am looking for further details on the Cisco documentation (I believe this scenario is called Inter-AS MPLS topology), but any comments would be more than welcome

Thanks in advance,