Alcatel-Lucent 7750 SR OS - Manual (Page 184)

VRRP Priority Control Policies
Page 184 7750 SR OS Router Configuration Guide
Each event generates a VRRP priority event message indicating the policy-id, the event type, the
priority type (delta or explicit) and the event priority value. Another log message is generated
when the event is no longer true, indicating that it has been cleared.
Priority Event Hold-Set Timers
Hold-set timers are used to dampen the effect of a flapping event. A flapping event is where the
event continually transitions between clear and set. The hold-set value is loaded into a hold set
timer that prevents a set event from transitioning to the cleared state until it expires.
Each time an event transitions between cleared and set, the timer is loaded and begins to count
down to zero. If the timer reaches zero, the event will be allowed to enter the cleared state once
more. Entering the cleared state is always dependent on the object controlling the event
conforming to the requirements defined in the event itself. It is possible, on some event types, to
have a further set action reload the hold set timer. This extends the amount of time that must expire
before entering the cleared state.
For an example of a hold-set timer setting, refer to LAG Degrade Priority Event on page 184 .
Port Down Priority Event
The port down priority event is tied to either a physical port or a SONET/SDH channel. The port or
channel operational state is evaluated to determine a port down priority event or event clear.
When the port or channel operational state is up, the port down priority event is considered false or
cleared. When the port or channel operational state is down, the port down priority event is
considered true or set.
LAG Degrade Priority Event
The LAG degrade priority event is tied to an existing Link Aggregation Group (LAG). The LAG
degrade priority event is conditional to percentage of available port bandwidth on the LAG.
Multiple bandwidth percentage thresholds may be defined, each with its own priority value.
If the LAG transitions from one threshold to the next, the previous threshold priority value is
subtracted from the total delta sum while the new threshold priority value is added to the sum. The
new sum is then subtracted from the base priority and compared to the delta in-use priority limit to
derive the new in-use priority on the virtual router instance.