CCIE Routing and Switching v5.1 Foundations: Bridging the Gap Between CCNP and CCIE

Chapter 15 MPLS and L3VPNs

Multiprotocol Label Switching (MPLS) is a label switching technology. With MPLS, instead of relying on IP addresses in the IP header to route packets, the router actually builds a label switching path, or LSP, for packets that require sustained forwarding treatment. This is also known as a forwarding equivalence class (FEC) and includes source destination IPs, IP precedents, and so on.

In the packet, we can switch based on the MPLS label that the packet carries, while the MPLS label itself is swapped along the way until the packet reaches the last MPLS router closest to the destination. Before the packet label switching can happen, the router needs to know what label to use, and that is through a label distribution ...