VRRP
Router Configuration Guide 383
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.
Port Down Priority Event
The port down priority event is tied to either a physical port or a SONET/SDH channel for
the 7750 SR and 7450 ESS. 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.
The following example illustrates a LAG priority event and it’s interaction with the hold set
timer in changing the in-use priority.
The following state and timer settings are used for the LAG events displayed in Table 32:
To Next Page
Loading...
