Virtual Router Redundancy Protocol (VRRP)
General Operation
■ When a VR is active you cannot change any of the following on that VR:
• priority
• advertisement interval
• preempt mode
• virtual IP address
■ A VR exists within a single VLAN interface. If the VLAN is multinetted,
then a separate VR can be configured within the VLAN for each sub-
net. A VLAN allows up to 32 VRs and the switch allows up to 2048 VRs.
■ All routers in the same VR must belong to the same network or subnet.
■ The router supports the following maximums:
• 32 VRs per VLAN in any combination of Masters and Backups
• 2048 VRs per router
• 32 IP addresses per VR
■ Each VR uses one MAC address as described under “Virtual Router
MAC Address” on page 6-10.
■ If an IP address is deleted on a VLAN interface, one of the following
occurs:
• VR Owner: If the VR uses the same IP address as a virtual IP address,
then that IP address is deleted from the VR.
• VR Backup: If the VR has a virtual IP address in the same subnet as
that of the deleted IP address, then that virtual IP address will be
deleted from the VR.
If the deleted virtual IP address was the last virtual IP address of an active
VR, then the VR will be deactivated. (For more on multiple, virtual IP
addresses on a VR, refer to “Associating More Than One Virtual IP Address
With a VR” on page 6-17.
■ The VRRP backup router does not respond to pings when it is in the
master role. This behavior is by design, and is required by section 6.4.3
of the VRRP RFC 3768. The backup router will forward traffic as
appropriate for its gateway role, but will not respond to ping. The
failed ping response is often an important mechanism for reporting
the failover which has occurred on the network segment.
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