Concept Guide
Figure 125. Uplink Failure Detection Example
If only one of the upstream interfaces in an uplink-state group goes down, a specied number of downstream ports associated with the
upstream interface are put into a Link-Down state. You can congure this number and is calculated by the ratio of the upstream port
bandwidth to the downstream port bandwidth in the same uplink-state group. This calculation ensures that there is no trac drops due to
insucient bandwidth on the upstream links to the routers/switches.
By default, if all upstream interfaces in an uplink-state group go down, all downstream interfaces in the same uplink-state group are put into
a Link-Down state.
Using UFD, you can congure 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 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 trac upstream, the server with NIC teaming detects the disabled link and
automatically switches over to the backup link in order.
Important Points to Remember
When you congure UFD, the following conditions apply.
• You can congure up to 16 uplink-state groups. By default, no uplink-state groups are created.
– 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 a physical port or port-channel interfaces to an uplink-state group.
– You can assign an interface to only one uplink-state group. Congure 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 congured minimum number of members parameter.
Uplink Failure Detection (UFD)
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