OSPF DR & BDR Election Process !!!

Why DR and BDR ?

• Consider, If you are having 50 Routers in multi-Access network, then you need to form a neighbor-ship with all OSPF Router, and send updates to all OSPF neighbors which might leads to huge congestion of Multicast Packets.
• In order to overcome this, DR and BDR process has been introduced in OSPF.
• If DR and BDR is Elected, All Routers will send updates only to DR and BDR, which reduces the Congestion of Multicast packets.

DR and BDR Characteristics

• OSPF uses a DR (Designated Router) and BDR (Backup Designated Router) on each multi-access network.
• DR and BDR Election is done per Multi-Access Network, & not per Area.
• DR & BDR is elected based on Priority(Higher the Priority is selected).
• If Priority is same, then the Router with highest IP Address will be Elected as DR.
• By default, OSPF has a default priority of 1.
• OSPF with the priority of 0, will not participate in DR and BDR Election.

Consider the Below Topology:





Let’s consider, If we want to make R1 as a DR,

That's it.