Avaya P580 - Manual (Page 390)

9-104 Avaya P550R, P580, P880, and P882 Multiservice Switch User Guide, v5.3.1
Chapter
Non-Address
Owner Features
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.
Assigning
Priorities to
Virtual Routers
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
associated IP Address. In other words, equal priorities are not
enough for a backup router that is already in the Primary state to
become Backup.