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Routing & Switching · Intermediate

Label Distribution Protocol (LDP)

A protocol that distributes label bindings for IGP prefixes between MPLS neighbors.

Definition

LDP discovers neighbors with UDP 646 hellos to 224.0.0.2 and forms sessions over TCP 646 from the LDP router ID (transport address). It uses downstream unsolicited distribution, independent control (Cisco) and liberal label retention. Labels follow the IGP best path.

Example

mpls ldp router-id Loopback0 force

Exam tip

The LDP router ID must be reachable via the IGP or the session will not establish.

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