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Configuring Interface Priority for PIM Designated Router Selection

A designated router (DR) sends periodic join messages and prune messages toward a group-specific rendezvous point (RP) for each group for which it has active members. When a Protocol Independent Multicast (PIM) routing device learns about a source, it originates a Multicast Source Discovery Protocol (MSDP) source-address message if it is the DR on the upstream interface.

By default, every PIM interface has an equal probability (priority 1) of being selected as the DR. Configuring the interface DR priority helps ensure that changing an IP address does not alter your forwarding model.

To configure the interface designated router priority:

  1. This example shows the configuration for the routing instance. Configure the interface globally or in the routing instance.
    [edit routing-instances PIM.master protocols pim interface ge-0/0/0.0 family inet]user@host# set priority 5
  2. Verify the configuration by checking the Hello Option DR Priority field in the output of the show pim neighbors detail command.
    user@host> show pim neighbors detail
    Instance: PIM.master
    Interface: ge-0/0/0.0
    Address: 192.168.195.37, IPv4, PIM v2, Mode: Sparse
    Hello Option Holdtime: 65535 seconds
    Hello Option DR Priority: 5
    Hello Option LAN Prune Delay: delay 500 ms override 2000 ms
    Join Suppression supported
    Rx Join: Group Source Timeout
    225.1.1.1 192.168.195.78 0
    225.1.1.1 0
    
    Interface: lo0.0
    Address: 10.255.245.91, IPv4, PIM v2, Mode: Sparse
    Hello Option Holdtime: 65535 seconds
    Hello Option DR Priority: 1
    Hello Option LAN Prune Delay: delay 500 ms override 2000 ms
    Join Suppression supported
    
    Interface: pd-6/0/0.32768
    Address: 0.0.0.0, IPv4, PIM v2, Mode: Sparse
    Hello Option Holdtime: 65535 seconds
    Hello Option DR Priority: 0
    Hello Option LAN Prune Delay: delay 500 ms override 2000 ms
    Join Suppression supported

Published: 2014-06-25