Cisco Enterprise Network Core Technologies (ENCOR) Practice Exam

VRRP, which stands for Virtual Router Redundancy Protocol, uses the multicast address 224.0.0.18 for its communications. This address is designated for VRRP traffic, allowing routers participating in the VRRP group to send and receive messages effectively.

When a router becomes the master in a VRRP setup, it sends advertisements to this multicast address to inform other routers in the group about its status and configuration. This approach ensures that all backups are aware of which router is currently in control of the virtual IP address, providing redundancy and failover capabilities in a network.

The other multicast addresses listed do not pertain specifically to VRRP. For instance, 224.0.0.5 is used for all routers on a local network segment, while 224.0.0.6 is used for all designated routers. Meanwhile, 239.255.255.255 is a reserved multicast address used in specific applications and is not related to VRRP functionalities. Understanding these addresses helps clarify the specific operational scope of VRRP within the larger context of networking protocols.