What is the primary function of the Designated Router (DR) in an OSPF network?

The primary function of the Designated Router (DR) in an OSPF network is to reduce OSPF routing information sent over the network. In OSPF, particularly in multi-access networks like Ethernet, each router will generally try to form adjacencies with all other routers. This can lead to a significant amount of routing information being exchanged, which can cause excessive traffic and overhead.

To mitigate this, OSPF designates one router as the DR, which is responsible for generating and sending Link-State Advertisements (LSAs) to other routers in the network. Instead of every router in the segment sending updates to every other router, the non-DR routers send their LSAs to the DR, which then propagates those LSAs to the other routers in the segment. This dramatically reduces the amount of OSPF traffic on the network and optimizes the routing process.

By minimizing the number of adjacencies and the amount of routing information exchanged, the DR plays a crucial role in maintaining OSPF efficiency and performance. This focused approach also helps ensure that the routing tables are kept up to date without overwhelming the network with too much redundant information.