One active master switch exists for each IP subnet. All other VRRP interfaces in a network are in backup mode.
Virtual Router Redundancy Protocol (VRRP) eliminates the single point of failure that can occur after the single static default gateway router for an end station is lost. VRRP introduces the concept of a virtual IP address shared between two or more routers connecting the common subnet to the enterprise network.
Note
The VRRP virtual IP address cannot be same as the local IP address of the port or VLAN on which VRRP is enabled.
Important
The switch, when it acts as a VRRP master, does not reply to Simple Network Management Protocol (SNMP) Get requests to the VRRP virtual interface address. However, if the switch acts as a VRRP master, and receives SNMP Get requests to its physical IP address, then it does respond.
The Simple Network Management Protocol (SNMP) provides facilities to manage and monitor network resources. An SNMP manager and agent communicate through the SNMP protocol. The manager sends queries and the agent responds. An SNMP Get request is a message that requests the values of one or more objects.
Note
The VRRP IP address responds only to ICMP-based traceroute requests. It does not respond to UDP-based traceroute requests.
When you use the fast advertisement interval option to configure a master and backup device, you must enable the fast advertisement interval option on both systems for VRRP to work correctly. If you configure one device with the regular advertisement interval, and the other device with the fast advertisement interval, it causes an unstable state and drops advertisements.