How Ospf Dr & Bdr Is Elected?

1.	How Ospf Dr & Bdr Is Elected?
Answer» The router with the highest priority becomes the DR and router with second highest priority becomes the BDR. If there is a tie in priority, router with the highest Router ID will become DR. By default priority on Cisco routers is 1. We can MANUALLY change it. If the Router priority is set to 0 (Zero), that router will not participate in DR/BDR ELECTION. DR election process is not preemptive. If a router with a higher priority is added to the NETWORK, it will not become DR untill we clear OSPF process and DR/BDR election takes place again. Command to change the priority on an interface router(config)# interface fa0/0 router(config-if)# ip ospf priority 100 Command to change the priority on an interface router(config)# interface fa0/0 router(config-if)# ip ospf priority 100

Answer»

The router with the highest priority becomes the DR and router with second highest priority becomes the BDR. If there is a tie in priority, router with the highest Router ID will become DR.
By default priority on Cisco routers is 1. We can MANUALLY change it.
If the Router priority is set to 0 (Zero), that router will not participate in DR/BDR ELECTION.
DR election process is not preemptive. If a router with a higher priority is added to the NETWORK, it will not become DR untill we clear OSPF process and DR/BDR election takes place again.

Command to change the priority on an interface

router(config)# interface fa0/0

router(config-if)# ip ospf priority 100

Command to change the priority on an interface

router(config)# interface fa0/0

router(config-if)# ip ospf priority 100

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