How DR/BDR gets elected in OSPF:
The purpose of having a DR and BDR is to reduce the amount of network traffic generated by OSPF, as only the DR and BDR exchange full routing information, while other routers only exchange minimal information. This helps ensure the stability and efficiency of the OSPF network.
The DR is responsible for managing the flow of routing information between routers in that segment, and for maintaining the integrity of the routing information.
The BDR acts as a backup for the DR, taking over if the DR fails or becomes unavailable.
Election Process:
The following steps outline the election process:
· -- The router with the highest priority becomes the DR. (Defaultpriority is 1)
· -- Router with second highest priority becomes BDR.
· -- If same priority, the router with the highest Router ID is elected as the DR.
Below Diagram all router has Same priority then router with Highest RID will become DR
Routerc will become DR because it has highest Loopback IP and Router B will be BDR
What is Router ID:
The router ID (RID) is 32-bit unique identifier assigned to each router in an OSPF network.
It is used by OSPF to identify the router in the network and to distinguish it from other routers.
is either assigned manually by the network administrator or automatically generated by the router
The RID is usually assigned using the highest IP address assigned to the router, either on a physical interface or a loopback interface
Commands to manual configure Router ID:
Points to be Noted:
· - If priority is “0” then router can’t be elected as a DR and BDR.
· -DR/BDR election process is non-preemptive means once routerselected as a DR and if new router comes with higher priority ospf DR/BDRelection will not happen
· Till we manually clear ospf process by using below command.
#clear ip ospf process
· We can check DR/BD status by using “#show ip ospf neighbor” command
