Administrator Guide

Using UFD, you can configure the automatic recovery of downstream ports in an uplink-state group when the
link status of an upstream port changes. The tracking of upstream link status does not have a major impact on
central processing unit (CPU) usage.
UFD and NIC Teaming
To implement a rapid failover solution, you can use uplink failure detection on a switch with network adapter
teaming on a server.
For more information, refer to Network Interface Controller (NIC) Teaming.
For example, as shown previously, the switch/ router with UFD detects the uplink failure and automatically
disables the associated downstream link port to the server. To continue to transmit traffic upstream, the
server with NIC teaming detects the disabled link and automatically switches over to the backup link in order
to continue to transmit traffic upstream.
Important Points to Remember
When you configure UFD, the following conditions apply.
• You can configure up to 16 uplink-state groups. By default, no uplink state groups are created in PMUX
mode and uplink state group 1 is created in Standalone and VLT modes.
• An uplink-state group is considered to be operationally up if it has at least one upstream interface
in the Link-Up state.
• An uplink-state group is considered to be operationally down if it has no upstream interfaces in the
Link-Up state. No uplink-state tracking is performed when a group is disabled or in an
Operationally Down state.
• You can assign physical port or port-channel interfaces to an uplink-state group in PMUX mode.
• You can assign an interface to only one uplink-state group. Configure each interface assigned to
an uplink-state group as either an upstream or downstream interface, but not both.
• You can assign individual member ports of a port channel to the group. An uplink-state group can
contain either the member ports of a port channel or the port channel itself, but not both.
• If you assign a port channel as an upstream interface, the port channel interface enters a Link-
Down state when the number of port-channel member interfaces in a Link-Up state drops below
the configured minimum number of members parameter.
• If one of the upstream interfaces in an uplink-state group goes down, either a user-configurable set of
downstream ports or all the downstream ports in the group are put in an Operationally Down state with
an UFD Disabled error. The order in which downstream ports are disabled is from the lowest numbered
port to the highest.
• If one of the upstream interfaces in an uplink-state group that was down comes up, the set of
UFD-disabled downstream ports (which were previously disabled due to this upstream port going
down) is brought up and the UFD Disabled error is cleared.
• If you disable an uplink-state group, the downstream interfaces are not disabled regardless of the state
of the upstream interfaces.
• If an uplink-state group has no upstream interfaces assigned, you cannot disable downstream
interfaces when an upstream link goes down.
• To enable the debug messages for events related to a specified uplink-state group or all groups, use the
debug uplink-state-group [group-id] command, where the group-id is from 1 to 16.
Uplink Failure Detection (UFD) 898