OSPF DR/BDR Election

On multi-access network segments (e.g., Ethernet), OSPF elects a Designated Router (DR) and a Backup Designated Router (BDR) to reduce the number of adjacencies and the amount of routing traffic.

Election Process:

  1. Highest OSPF Priority: Router with the highest OSPF priority (0-255) becomes DR. If tied, then highest Router ID wins.
  2. Highest Router ID: If priorities are equal, the router with the highest Router ID becomes DR.
  3. Non-Preemptive: Once a DR/BDR is elected, it remains DR/BDR unless it fails or is manually reset.

Configuration:

interface GigabitEthernet0/0
 ip ospf priority [0-255]
  • Priority 0 means the router will never become DR or BDR.