Dell Force10 S4820T S4820T Configuration Guide - Page 467

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 state or flaps, routing protocols are notified of the status of the routes that are affected by the change in state, and these protocols go through 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 flapping by imposing a penalty for each interface flap and decaying the penalty exponentially. Once the penalty exceeds 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." Once 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 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 • Link dampening can be applied to Layer 2 and Layer 3 interfaces. • Link dampening can be configured on individual interfaces in a LAG. Enable Link Dampening Enable link dampening using the command dampening from INTERFACE mode, as shown in the following example. R1(conf-if-gi-1/1)#show config ! interface GigabitEthernet 1/1 ip address 10.10.19.1/24 dampening 1 2 3 4 no shutdown R1(conf-if-gi-1/1)#exit Interfaces | 467