Which two network types in OSPF elect a designated router (DR)?

In OSPF (Open Shortest Path First), the designated router (DR) is elected in specific types of network topologies to optimize routing by reducing the amount of routing information exchanged. The network types that elect a DR are typically those that can form a multi-access environment where multiple routers share a common subnet and would otherwise create excessive routing traffic.

Broadcast networks, such as Ethernet, enable multiple devices to communicate directly with one another. Because several routers can connect to the same broadcast medium, the election of a DR allows these routers to consolidate and communicate OSPF routing information effectively, thus minimizing routing overhead.

Nonbroadcast multi-access (NBMA) networks, such as Frame Relay, also require a DR election. In a nonbroadcast environment, there is no inherent capability for multi-access communication, which would necessitate establishing adjacencies individually. The DR in this case helps facilitate communication among multiple routers in a way that reduces the complexity and control traffic.

In contrast, point-to-point networks directly connect two routers, so each device communicates with the other without the need for a DR since there’s no multi-access requirement. Point-to-multipoint networks can operate similarly, allowing links to be treated as individual point-to-point links rather than relying on a