Dell PowerSwitch S4820T 9.50.1 Configuration Guide for the S4820T System - Page 438
Link Dampening, Important Points to Remember, Enabling Link Dampening
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NOTE: In the following show inventory media command output, the port numbers 1, 2, 3, 5, 6, and 7 ports are actually inactive. However, Dell Networking OS still shows that optical cables are inserted into these ports. This is a software limitation for this release. Dell# show inventory media Slot Port Type Media Serial Number 0 0 SFP+ 10GBASE-SX APF12420031B3P 0 1 SFP+ 10GBASE-SX APF12420031B3P 0 2 SFP+ 10GBASE-SX APF12420031B3P 0 3 SFP+ 10GBASE-SX APF12420031B3P 0 4 SFP 10GBASE-SX APF12420031B3P 0 5 SFP 10GBASE-SX APF12420031B3P 0 6 SFP 10GBASE-SX APF12420031B3P 0 7 SFP 10GBASE-SX APF12420031B3P 0 8 QSFP 4x10GBASE-CR1-3M APF12420031B3P 0 9 QSFP 4x10GBASE-CR1-3M APF12420031B3P 0 10 QSFP 4x10GBASE-CR1-3M APF12420031B3P 0 11 QSFP 4x10GBASE-CR1-3M APF12420031B3P 0 12 QSFP 40GBASE-SR4 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 reconverging. 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. 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 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. Enabling Link Dampening To enable link dampening, use the following command. 438 Interfaces
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