DELL 9.7(0.0) User Manual

56

Uplink Failure Detection (UFD)

Uplink failure detection (UFD) provides detection of the loss of upstream connectivity and, if used with 
network interface controller (NIC) teaming, automatic recovery from a failed link.

Feature Description

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.

Uplink Failure Detection (UFD)

903