MPLS Fundamentals: 3 – LDP

Basic MPLS LDP Configuration

224.0.0.2 group IP multicast address. The UDP port used for LDP is 646.

LDP Discovery

show mpls ldp discovery detail
show mpls ldp discovery detail
show mpls interfaces
show mpls interfaces

LDP discovery timers manipulation

mpls ldp discovery {hello {holdtime | interval } seconds

The default value for holdtime is 15 seconds for link Hello messages, and the default value for interval is 5 seconds.
If the two LDP peers have different LDP Hold times configured, the smaller of the two values is used as the Hold time for that LDP discovery source.

Cisco IOS might overwrite the configured LDP Hello interval. It will choose a smaller LDP Hello interval than configured so that it can send at least three LDP Hellos before the Hold time expires. (At least nine Hellos are sent in the case of a targeted LDP session)

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