MPLS LDP troubleshooting

When your MPLS neighbors are not forming the neighborship, you may have these possible issues:

  • MPLS IP not enabled on interface
  • protocol missmatch (TDP, LDP globaly or at interface level)
  • higher loopback ID is taken as a router ID which is not advertised via IGP
  • missmatch authentication if configured
  • filtering udp port 646 for LDP
  • etc

Commands to verify

  • show mpls interfaces
  • show mpls ldp neigh
  • show run int {xxx}
  • show run | sec mpls
  • trace XXX