Q1. What does DR do?

Reply: DR (Designated Router) represents router nodes on a broadcast subnet (e.g., Ethernet). It does:

  1. Create a Community LSA to explain nodes which can be hooked up to the subnet (known as hooked up routers.
  2. Synchronize LSDB with different hooked up routers on the subnet. (The companion simulation visualizes LSDB synchronization actions. )

Q2. What number of LSAs will routers outdoors the subnet see?

Reply: 5. on this state of affairs, there are four routers hooked up to the subnet. Every creates a Router LSA. When DR is being elected, it creates Community LSA. After DR and non-DR nodes are synchronized, all of them have 5 LSAs.

When the subnet gateway router have synchronized its LSDB with neighboring routers not hooked up to the subnet, outdoors nodes will see 5 LSAs from the subnet: 4 Router LSA, one Community LSA. (You’ll find the topology within the companion topology).  192.168 ll

Q3. Why do we want DR

Reply: Scalability.Contemplate an instance: If there are 10 OSPF routers (R1~ R10) hooked up to a subnet. To synchronize LSDBs, OSPF wants to take care of 45 two-way relationships (10*9/2=45). It is a advanced activity and consumes plenty of community sources. If we elect one as DR and solely DR maintains two-way relationships with the opposite 9 nodes then LSDB synchronization activity are tremendously lowered.