PIM DR Priority

The DR_Priority option allows a network administrator to give preference to a particular router in the DR election process by giving it a numerically larger DR Priority. The DR_Priority option is included in every Hello message, even if no DR Priority is explicitly configured on that interface. This is necessary because priority-based DR election is only enabled when all neighbors on an interface advertise that they are capable of using the DR_Priority Option. The default priority is 1.

DR Priority is a 32-bit unsigned number, and the numerically larger priority is always preferred. A router's idea of the current DR on an interface can change when a PIM Hello message is received, when a neighbor times out, or when a router's own DR Priority changes. If the router becomes the DR or ceases to be the DR, this will normally cause the DR Register state machine to change state. Subsequent actions are determined by that state machine.

The DR election process on the interface consists of the following:
  • If any one of the neighbors on the interface is not advertised, the DR priority (not DR capable) will not considered for the all the neighbors in the circuit and the primary IP address will be considered for all the neighbors.
  • Higher DR priority or higher primary address will be elected as DR.
Use the following command to configure PIM DR Priority:

configure pim {ipv4 | ipv6} {vlan} [vlan_name] dr-priority priority