Reference Guide

Uplink Failure Detection (UFD)

Uplink failure detection (UFD) is supported on the S4820T platform.

Feature Description

UFD provides detection of the loss of upstream connectivity and, if used with network interface controller (NIC) teaming,

automatic recovery from a failed link.

A switch provides upstream connectivity for devices, such as servers. If a switch loses its upstream connectivity,

downstream devices also lose their connectivity. However, the devices do not receive a direct indication that upstream

connectivity is lost because connectivity to the switch is still operational

UFD allows a switch to associate downstream interfaces with upstream interfaces. When upstream connectivity fails,

the switch disables the downstream links. Failures on the downstream links allow downstream devices to recognize the

loss of upstream connectivity.

For example, as shown in the following illustration, Switches S1 and S2 both have upstream connectivity to Router R1

and downstream connectivity to the server. UFD operation is shown in Steps A through C:

• In Step A, the server configuration uses the connection to S1 as the primary path. Network traffic flows from the

server to S1 and then upstream to R1.

• In Step B, the upstream link between S1 and R1 fails. The server continues to use the link to S1 for its network

traffic, but the traffic is not successfully switched through S1 because the upstream link is down.

• In Step C, UFD on S1 disables the link to the server. The server then stops using the link to S1 and switches to

using its link to S2 to send traffic upstream to R1.

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