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4
Configuring the Label Distribution
Protocol
This chapter describes the Label Distribution Protocol (LDP) and covers the following
topics:
• Overview of LDP on page 4-1
• Configuring LDP on page 4-3
• Configuration Example on page 4-10
Overview of LDP
The Label Distribution Protocol (LDP) is a protocol defined by the IETF for the purpose
of establishing an MPLS LSP. Using LDP, peer LSRs exchange label binding information
to create the LSP.
LDP Neighbor Discovery
LDP includes a neighbor discovery protocol that runs over UDP. Using the basic
discovery mechanism, each LSR periodically multicasts a hello message to a
well-known UDP port to which all LSRs listen. These hello messages are transmitted to
the all routers on this subnet multicast group. When a neighbor is discovered, a
hello-adjacency is formed and the LSR with the numerically greater IP address is
denoted as the active LSR.
MPLS Module Installation and User Guide
4-1
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