Dell EMC SmartFabric OS10 User Guide Release 10.5.0

Uplink Failure Detection

Uplink failure detection (UFD) indicates the loss of upstream connectivity to servers connected to the switch.

A switch provides upstream connectivity for devices, such as servers. If the switch loses upstream connectivity, the downstream devices also lose connectivity. However, the downstream devices do not generally receive an indication that the upstream connectivity was lost because connectivity to the switch is still operational. To solve this issue, use UFD.

UFD associates downstream interfaces with upstream interfaces. When upstream connectivity fails, the switch operationally disables its downstream links. Failures on the downstream links allow downstream devices to recognize the loss of upstream connectivity. This allows the downstream servers to select alternate paths, if available, to send traffic to upstream devices.

UFD creates an association between upstream and downstream interfaces known as uplink-state group. An interface in an uplink-state group can be a physical Ethernet or fibre channel interface or a port-channel.

An enabled uplink-state group tracks the state of all assigned upstream interfaces. The failure of upstream interfaces results in automatic disabling of downstream interfaces in the uplink-state group, as shown in the following illustration. If only one of the upstream interfaces in an uplink-state group goes down, a specific number of downstream interfaces in the same uplink-state group go down. You can configure the number of downstream interfaces that go down based on the traffic conditions from the server to the upstream interfaces. This avoids overloading traffic on upstream ports.

By default, if all the upstream interfaces in an uplink-state group go down, all the downstream interfaces in the same uplink-state group are set into a link-down state.

In addition, in an uplink-state group, you can configure automatic recovery of downstream ports when there is a change in the link status of uplink interfaces.

You can also bring up downstream interfaces that are in an UFD-disabled error state manually.

UFD Topology