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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 aps, routing protocols are notied of the status of the routes that are aected 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.
Link dampening minimizes the risk created by apping by imposing a penalty for each interface ap and decaying the penalty exponentially.
After the penalty exceeds a certain 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, the interface
comes up again and the routing protocols re-converge.
Link dampening:
• reduces processing on the CPUs by reducing excessive interface apping.
• improves network stability by penalizing misbehaving interfaces and redirecting trac.
• 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 congured for port monitoring.
• You can apply link dampening to Layer 2 and Layer 3 interfaces.
• You can congure link dampening on individual interfaces in a LAG.
Enabling Link Dampening
To enable link dampening, use the following command.
• Enable link dampening.
INTERFACE mode
dampening
Examples of the show interfaces dampening Commands
R1(conf-if-te-1/1)#show config
!
interface TengigabitEthernet 1/1
ip address 10.10.19.1/24
dampening 1 2 3 4
no shutdown
R1(conf-if-te-1/1)#exit
To view the link dampening conguration on an interface, use the show config command.
To view dampening information on all or specic dampened interfaces, use the show interfaces dampening command from EXEC
Privilege mode.
Dell# show interfaces dampening
Interface State Flaps Penalty Half-Life Reuse Suppress Max-Sup
Te 0/0 Up 0 0 57 502 500 20
Te 0/1 Up 2 1 200 20500 1500 300
Te 0/2 Down 4 8 50 30600 2000 120
466
Interfaces