Which multicast address is designated for all RIP routers?

The correct multicast address designated for all RIP (Routing Information Protocol) routers is 224.0.0.9. This address is specifically used for RIP version 1 and RIP version 2, allowing routers running RIP to exchange routing information efficiently without needing to address each router individually.

Using this multicast address means that messages sent to 224.0.0.9 will be received by all routers that have configured RIP, enabling them to update their routing tables based on the shared information. This efficient method of communication helps reduce network traffic compared to broadcasting updates to all devices.

Other multicast addresses mentioned serve different protocols or purposes. For example, 224.0.0.10 is used for the Cisco-Group Multicast address in the context of EIGRP (Enhanced Interior Gateway Routing Protocol), while 224.0.0.2 is meant for multicast routing for all routers in the network, and 224.0.0.5 is used by OSPF (Open Shortest Path First) for designated routers and backup designated routers. Each of these addresses is tailored specifically to their respective protocols rather than to RIP.