KB.15.15

VRRP packets.

Syntax:

[no] debug vrrp

Displays VRRP debug messages.

General operation

License requirements:

In the 3500yl, 3800, 5400zl, 6600, and 8200zl switches, VRRP is included with the Premium

License. In the 6200yl switches, this feature is included with the base feature set.

VRRP supports router redundancy through a prioritized election process among routers configured

as members of the same virtual router (VR.)

On a given VLAN, a VR includes two or more member routers configured with a VIP that is also

configured as a real IP address on one of the routers, plus a virtual router MAC address. The router

that owns the IP address is configured to operate as the owner of the VR for traffic-forwarding

purposes and by default has the highest VRRP priority in the VR. The other routers in the VR have

a lower priority and are configured to operate as backups in case the owner router becomes

unavailable.

The owner normally operates as the master for a VR. But if it becomes unavailable, then a failover

to a backup router belonging to the same VR occurs, and this backup becomes the current master.

If the owner recovers, a failback occurs and "master" status reverts to the owner. (Using more than

one backup provides additional redundancy" if both the owner and the highest-priority backup

fail, another, lower-priority backup can take over as master.)

NOTE:

• The VIP used by all VRRP routers in a VR instance is a realIP address that is also configured

on the applicable VLAN interface on the VR's owner router.

• The same MAC and VIPs are included in the VRRP configuration for the owner and all backup

routers belonging to the same VR and are used as the source addresses for all traffic forwarded

by the VR.

Figure 53 (page 275) shows a VR on VLAN 100 supported by Router 1 (R1) and Router 2 (R2.)

274 Virtual Router Redundancy Protocol (VRRP)