Nokia IPSO 4.0 Reference Manual page 189

Priority Delta
Choose a value for the priority delta that ensures that the priority delta subtracted from the
priority results in an effective priority that is lower than that of the backup routers (in case an
interface fails).
You might find it useful to use a standard priority delta throughout your VRRP configurations to
keep your configurations simple and easy to understand.
This parameter applies only to monitored-circuit VRRP, not to VRRPv2.
Backup Address
Also called the virtual IP address, the backup address is the IP address your end hosts and
neighbor routers use for routing. The backup address is the address that is failed over between
the master and the backup platforms. The backup address parameter is added to standard VRRP
for use with Nokia's monitored-circuit VRRP. It does not apply to VRRPv2.
The backup address must be in the same network as the interface you want to use for the VRID.
When you enter a backup address, the system uses the interface that is in that subnet for the
VRID.
Note
If there is no interface configured on the subnet of the backup address, the system does not
always display an error message. Verify that the backup address subnet is configured on
your system.
You must also select backup addresses that do not match the real IP address of any device on the
interface network nor the IP address of any of the interfaces on either VRRP node.
Before you modify backup addresses or delete an IP address from an interface, consider the
following points. (These points apply only to monitored-circuit VRRP configured using the
simplified method.)
You must manually modify the list of backup addresses on each node of a VRRP group
whenever the IP addresses of the other routers change.
You cannot change the backup address from one interface to another interface while a
platform is in the master state. To modify a virtual IP address, first cause a failover to the
backup (you can do this by disabling one of the VRRP-configured interfaces), then delete
the VRID and re-create it using the new IP address, then configure it as it was configured
before.
Before you delete an IP address from a logical interface, you must delete the corresponding
backup addresses configured for monitored-circuit VRRP. The configuration for the virtual
router might become corrupted if you delete the IP address before you delete the backup
addresses. This issue does not apply either to the full method configuration of
monitored-circuit VRRP or to VRRPv2.
Nokia Network Voyager for IPSO 4.0 Reference Guide 189