Alcatel-Lucent 7750 SR OS - Manual (Page 175)

VRRP
7750 SR OS Router Configuration Guide Page 175
When the IP address on the IP interface matches the virtual router IP address (owner mode), the
priority value is fixed at 255, the highest value possible. This virtual router member is considered
the owner of the virtual router IP address. There can only be one owner of the virtual router IP
address for all virtual router members.
The priority value 0 is reserved for VRRP advertisement message purposes. It is used to tell other
virtual routers in the same VRID that this virtual router is no longer acting as master, triggering a
new election process. When this happens, each backup virtual router sets its master down timer
equal to the skew time value. This shortens the time until one of the backup virtual routers
becomes master.
The current master virtual router must transmit a VRRP advertisement message immediately upon
receipt of a VRRP message with priority set to 0. This prevents another backup from becoming
master for a short period of time.
Non-owner virtual routers may be configured with a priority of 254 through 1. The default value is
100. Multiple non-owners can share the same priority value. When multiple non-owner backup
virtual routers are tied (transmit VRRP advertisement messages simultaneously) in the election
process, both become master simultaneously, the one with the best priority will win the election. If
the priority value in the message is equal to the master’s local priority value, then the primary IP
address of the local master and the message is evaluated as the tie breaker. The higher IP address
becomes master. (The primary IP address is the source IP address of the VRRP advertisement
message.)
The priority is also used to determine when to preempt the existing master. If the preempt mode
value is true, VRRP advertisement messages from inferior (lower priority) masters are discarded,
causing the master down timer to expire and the transition to master state.
The priority value also dictates the skew time added to the master timeout period.
IP Addresses
Each virtual router participating in the same VRID should be defined with the same set of IP
addresses. These are the IP addresses being used by hosts on the LAN as gateway addresses. Since
multi-netting supports 16 IP addresses on the IP interface, up to 16 addresses may be assigned to a
specific a virtual router instance.