What is the multicast IPv4 address used by HSRPv1?

HSRP, or Hot Standby Router Protocol, utilizes specific multicast IP addresses for its operation. In the case of HSRPv1, the designated multicast address is 224.0.0.2. This address is used for sending Hello packets between routers configured for HSRP to identify which router will act as the Active or Standby router for a virtual router.

The choice of 224.0.0.2 is significant because it is specifically reserved for all routers within the local subnet and is essential for establishing communication among the routers participating in HSRP. Each router that needs to participate in the HSRP group sends its messages to this multicast address, ensuring that all routers in the same HSRP group listen to and respond to the messages.

Understanding this multicast address is crucial for network engineers working with redundancy and failover scenarios, ensuring high availability in IP networking environments.