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Virtual Router Redundancy Protocol
Virtual Router Redundancy Protocol (VRRP) allows you to configure a
group of routers as a single virtual router. The virtual router group is
configured with a single virtual IP address that can be used as the default
gateway for host devices on the attached network.
Configuring VRRP Groups
To configure VRRP, select an interface on one router in the group to serve
as the master virtual router. This physical interface is used as the virtual
address for the router group. Now set the same virtual address and a
priority on the backup routers, and configure an authentication string. You
can also enable the preempt feature which allows a router to take over as
the master router when it comes on line.
Command Usage
Address Assignment –
• The IP address assigned to the virtual router must already be configured
on the router that will be the Owner. In other words, the IP address for
the virtual router exists on one, and only one, router in the virtual router
group, and the network mask for the virtual router address is derived
from the Owner. The Owner will also assume the role of the Master
virtual router in the group.
• If you have multiple secondary addresses configured on the current
VLAN interface, you can add any of these addresses to the virtual router
group.
• The interfaces of all routers participating in a virtual router group must
be within the same IP subnet.
• VRRP creates a virtual MAC address for the master router based on a
standard prefix, with the last octet equal to the group ID. When a backup
router takes over as the master, it continues to forward traffic addressed
to this virtual MAC address. However, the backup router cannot reply to
ICMP pings sent to addresses associated with the virtual group because
the IP address owner is off line.