Which multicast address represents all OSPF routers?

The correct choice represents the multicast address specifically designated for all OSPF routers, which is 224.0.0.5. This address is used for OSPF routing protocols to allow all OSPF-enabled devices on a local network segment to receive OSPF routing updates and advertisements.

This address enables routers that are running OSPF to communicate efficiently without the need to send packets to each individual router, thus reducing the overall network traffic and enhancing performance. When an OSPF router sends updates to this multicast address, all OSPF routers on that local broadcast domain will receive the information.

In other multicast addresses related to OSPF, 224.0.0.10 is used for the Designated Router (DR) and Backup Designated Router (BDR) within an OSPF network segment, servicing more specific routing roles rather than addressing all routers. 224.0.0.6 is used for OSPF routers that are designated as inactive or in a special role, and 224.0.0.1 is a general multicast address used for all multicast-capable hosts, which pertain to a broader category than just OSPF routers.

Understanding these multicast addresses helps in grasping how