Install Guide

For these configurations, the following examples show the command output that the show interfaces
tengigbitethernet transceiver, show interfaces tengigbitethernet, and show inventory media
commands displays:
NOTE: In the following show interfaces tengigbitethernet commands, the ports 1,2, and 3 are inactive and no
physical SFP or SFP+ connection actually exists on these ports. However, Dell Networking OS still perceives these ports as
valid and the output shows that pluggable media (optical cables) is inserted into these ports. This is a software limitation for
this release.
Link Dampening
Interface state changes occur when interfaces are administratively brought up or down or if an interface state changes.
Every time an interface changes a state or flaps, routing protocols are notified of the status of the routes that are affected by
the change in state. These protocols go through the momentous task of re-converging. Flapping; therefore, puts the status of
entire network at risk of transient loops and black holes. Dampening limits the notification of status to the routing protocols.
Link dampening minimizes the risk created by flapping by imposing a penalty (1024) for each interface flap and decaying the
penalty exponentially based on the half-time. When the accumulated penalty exceeds a certain threshold (suppress threshold),
the interface is put in an Error-Disabled state and for all practical purposes of routing, the interface is deemed to be “down.”
After the interface becomes stable and the penalty decays below a certain threshold (reuse threshold), the interface comes up
again and the routing protocols re-converge.
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.
Interfaces
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