Master Down Interval; Preempt Mode - Alcatel-Lucent 7450 Configuration Manual

Master Down Interval

The master down interval is a calculated value used to load the master down timer. When the
master down timer expires, the virtual router enters the master state. To calculate the master down
interval, the virtual router evaluates the following formula:
The operational advertisement interval is dependent upon the state of the inherit parameter. When
the inherit parameter is enabled, the operational advertisement interval is derived from the current
master's advertisement interval field in the VRRP advertisement message. When inherit is
disabled, the operational advertisement interval must be equal to the locally configured
advertisement interval.
The master down timer is only operational when the local virtual router is operating in backup
mode.

Preempt Mode

Preempt mode is a true or false configured value which controls whether a specific backup virtual
router preempts a lower priority master. The IP address owner will always become master when
available. Preempt mode cannot be set to false on the owner virtual router. The default value for
preempt mode is true.
When preempt mode is true, a master non-owner virtual router will only allow itself to be
preempted when the incoming VRRP advertisement message priority field value is one ot the
following:
•
•
A backup router will only attempt to become the master router if the preempt mode is true and the
received VRRP advertisement priority field is less than the virtual router in-use priority value.
7450 ESS Router Configuration Guide
Master Down Interval = (3 x Operational Advertisement Interval) + Skew Time
Greater than the virtual router in-use priority value
Equal to the in-use priority value and the source IP address (primary IP address) is greater
than the virtual router instance primary IP address
VRRP
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