O'Reilly logo

MPLS Fundamentals by Luc De Ghein - CCIE No. 1897

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

Verifying Label Switched Path

A label switched path (LSP) can fail at any given place in the network. You can verify the LSP step by step by looking at the IP routing protocols and label distribution protocols (LDP, RSVP, and BGP) and by looking at the Cisco Express Forwarding (CEF) table and label forwarding information base (LFIB) on the provider edge (PE) and provider (P) routers. At a minimum, the LSP must never be interrupted; this means that the LSP must always have an incoming label and an outgoing label in the LFIB pointing to the correct next-hop label switching router (LSR). As soon as the outgoing label is “No Label” (Untagged) at an LSR that is not the egress LSR, the packets are forwarded unlabeled, and the packet forwarding fails ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required