Avaya Cajun P882 User Manual page 382

Chapter 9
Non-Address
Owner Features
Assigning
Priorities to
Virtual Routers
9-100
Preempt mode cannot be disabled. A virtual router that is IP
Address Owner will always preempt and assume Mastership
from a Backup router.
A virtual router that is IP Address Owner will "overwrite" the
MAC Address of the associated IP Address. In the ARP Cache
Table, the MAC Address of the IP Address will be the VRRP
MAC.
Non-address owner features are:
Requires more configuration but allows for more control and
customization of the Priorities of each virtual router.
The virtual router IP Address and associated IP Address will both
be displayed in the ARP Cache Table. This is helpful for
troubleshooting and identification.
Preempt Mode can be used. As described in the "IP Address
Owner Features" section, if the Preempt Mode is set to False,
then a higher Priority virtual router will not assume Mastership
from a virtual router that is currently Master. This is helpful
when a router goes down and the Backup router becomes
Master. When the original router comes back online, it will not
take Mastership from the current Master. This will allow the
current traffic to remain unchanged. Another state change will
only occur if the current Master router goes down. This is
especially helpful in a network where a routing protocol is used
(RIP, OSPF). In most cases, the VRRP election process will take
place before the routing table has been updated. This may
cause a longer period of traffic loss.
The allowed configurable range for the Priority of a virtual router is
1-254. 255 is reserved for a virtual router that is IP Address Owner
(as described above). If two routers are participating in VRRP,
making the desired Master router 254 (or 255 if IP Address Owner)
and the Backup router 100 (the default Priority) is a common
configuration. If multiple routers will be backing up the Master
router, then the Priorities can be assigned in descending order (100,
99, 98, etc., for example).
Equal Priorities are also allowed but may be more difficult to
troubleshoot. If two Master routers have the same Priority (and the
same VRRP settings), the VRRP election process then checks the
associated IP Address of each virtual router. In that case, the
associated IP Address with a higher value becomes Master.
However, if a Master and Backup virtual router have the same
Priority, the Backup will not become Master even if it has a higher
Avaya P550R, P580, P880, and P882 Multiservice Switch User Guide, v5.3.1