An engineer configured an OSPF neighbor as a designated router.
Which state verifies the designated router is in the proper mode?
When an OSPF neighbor is configured as a designated router (DR), it transitions through several states to establish and maintain adjacency with other routers in the network. These states are known as the OSPF neighbor states.
The correct answer to this question is option C: Exchange.
The Exchange state is the third state in the OSPF neighbor relationship establishment process, after the 2-way state. In this state, the routers exchange information about the LSAs (link-state advertisements) in their respective databases. This information includes the router ID, the LSAs, and the sequence number of the LSAs. This information is exchanged in the form of Database Description (DBD) packets.
During this exchange, the designated router will advertise itself as the DR and the backup designated router (BDR). The other routers in the network will then acknowledge the DR and BDR by sending back a message to confirm.
Once this exchange is completed successfully, the OSPF neighbor relationship will move to the next state, which is the Full state. In this state, the routers have established a full adjacency, and they are ready to exchange routing updates.
Therefore, the Exchange state verifies that the designated router is in the proper mode as it involves the DR advertising itself to other routers and receiving confirmation from them.