Administrator Guide

You configure link dampening using the dampening [[[[half-life] [reuse-threshold]] [suppress-threshold]]
[max-suppress-time]] command on the interface.
Following is the detailed explanation of interface state change events:
• suppress-threshold— The suppress threshold is a value that triggers a flapping interface to dampen. The system adds penalty
when the interface state goes up and down. When the accumulated penalty reaches the default or configured suppress threshold, the
interface state changes to Error-Disabled state. The range of suppress threshold is from 1 to 20000. The default is
2500.
•
half-life— The accumulated penalty decays exponentially based on the half-life period. The accumulated penalty decreases half
after each half-life period. The range of half-life is from 1 to 30 seconds. The default is 5 seconds.
• reuse-threshold— After exponential decay, the penalty reaches the default or configured reuse threshold. The interface is
unsuppressed and the state changes to “up”. The range of reuse threshold is from 1 to 20000. The default is 750.
• max-suppress-time— The maximum amount of time during which the interface remain suppressed. The range is from 1 to 86400.
The default is 20 seconds or four times the default half-life period (5 seconds).
NOTE:
suppress-threshold should be greater than reuse-threshold.
max-suppress-time should be at least 4 times half-life.
Link dampening:
• reduces processing on the CPUs by reducing excessive interface flapping.
• improves network stability by penalizing misbehaving interfaces and redirecting traffic.
• improves convergence times and stability throughout the network by isolating failures so that disturbances are not propagated.
Important Points to Remember
• Link dampening is not supported on VLAN interfaces.
• Link dampening is disabled when the interface is configured for port monitoring.
• You can apply link dampening to Layer 2 and Layer 3 interfaces.
• You can configure link dampening on individual interfaces in a LAG.
Configuration Example of Link Dampening
The figure shows a how link dampening works in a sample scenario when an interface is configured with dampening. The following figure
shows the interface state change, accumulation and decay of penalty, and the interface advertised state based on the set dampening
parameters. The dampening parameters are set as follows:
• half-life— 10 seconds
• reuse-threshold—300
• suppress-threshold—2400
• max-suppress-time—60 seconds
328
Interfaces