Q1. What does DR do?
Reply: DR (Designated Router) represents router nodes on a broadcast subnet (e.g., Ethernet). It does:
- Create a Community LSA to explain nodes which can be hooked up to the subnet (known as hooked up routers.
- 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.