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DES-7200 Configuration Guide Chapter 1 Protocol-Independent
Configuration
1-12
1.4.2 Interface State Change Events
The feature of IP Event Dampening perceives and controls interface behavior by
adopting a mechanism of calculating the penalty upon any change in interface
state. Each up-down flapping of interface will lead to the accumulation of
penalties. When the interface stabilizes, the penalties will decrease exponentially.
Through such penalty calculation, the interface can intelligently perceive its own
state and take corresponding measures. Figure 1 is a chart that displays interface
state events as they are perceived by upper layer routing protocols. This
suppression algorithm is actually the application of route flap suppression
algorithm (RFC2439) on network interface state.
1.4.2.1 Suppress Threshold
This value is the threshold configured for the accumulated penalty in order to
identify interface flapping. When the value of accumulated penalty exceeds this
threshold, the interface is considered flapping and will be dampened.
1.4.2.2 Half-Life Period
The half-life period refers to the time required for the penalty to decay to the half
value when the interface is stable. It determines how fast the accumulated
penalty can decay exponentially. The shorter the half-life period is, the faster the
decaying and stable interface detection will be, but the sensitivity to flap detection
will become lower. The default half-life period timer is 5 seconds.
Fig 1 Interface state change event perceived by the routing protocols