How MPLS Works: Front page of MPLS newspaper

This document mainly explains the following:

MPLS header structure and the role of each primary field.

How the tagged message is forwarded

Keep the MPLS tag names, as well as their role.

Determines the importance of MPLS MTU in MPLS networks.

In MPLS, they are exchanged/push/pop with tags for data forwarding.

The label has three modes of operation: Swap/Add/Remove

When a router receives an IP message, the lookup is IP lookup. In Cisco IOS, the message for IP lookup is the CEF (Cisco Express forwarding) lookup. When a router receives a tagged message, the lookup is done in the lfib of the router. (show Mpls forwarding-table).

by LFIB (Tag lookup), the message should be tagged when it leaves the router.

The following is to find the CEF table IP message forwarding and lookup LFIB table MPLS message forwarding operations.