HP 3500YL - Manual (Page 340)

Virtual Router Redundancy Protocol (VRRP)
General Operation
Owner Router
An Owner router for a VR is the default Master router for the VR, and operates
as the Owner for all subnets included in the VR. As mentioned earlier, the
VRRP priority on an Owner router is always 255 (the highest).
N o t e On a multinetted VLAN where multiple subnets are configured in the same
VR, the router must be either the Owner for all subnets in the VR or a Backup
for all subnets in the VR.
Backup Router
There must be at least one Backup router. A given VR instance on a Backup
router must be configured with the same virtual IP address as the Owner for
that VR (and both routers must belong to the same network or subnet). Router
2 in figure 6-1 on page 6-6 illustrates this point.
VR Priority Operation. In a Backup router’s VR configuration, the virtual
router priority defaults to 100. (The priority for the configured Owner is
automatically set to the highest value; 255.) In a VR where there are two or
more Backup routers, the priority settings can be reconfigured to define the
order in which Backups will be reassigned as Master in the event of a failover
from the Owner.
Preempt Mode. Where multiple Backup routers exist in a VR, if the current
Master fails and the highest-priority Backup is not available, then VRRP selects
the next-highest priority Backup to operate as Master. If the highest-priority
Backup later becomes available, it pre-empts the lower-priority Backup and
takes over the Master function. If you don’t want a Backup router to have this
preemptive ability on a particular VR, you can disable this operation with the
no preempt-mode command. (Note that Preempt Mode applies only to VRRP
routers configured as Backups.) Refer to “Preempt Mode on VRRP Backup
Routers” on page 6-25.
Virtual Router MAC Address
When a VR instance is configured, the protocol automatically assigns a MAC
address based on the standard MAC prefix for VRRP packets, plus the VRID
number (as described in RFC 3768). The first five octets form the standard
MAC prefix for VRRP, and the last octet is the configured VRID. That is:
00-00-5E-00-01-< VRid >
For example, the virtual router MAC address for the VR in figure 6-1 on page
6-6 is 00-00-5E-00-01-01.
6-10