Reference Guide

Figure 128. Uplink Failure Detection Example
If only one of the upstream interfaces in an uplink-state group goes down, a specified number of downstream ports
associated with the upstream interface are put into a Link-Down state. You can configure 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 traffic drops due to insufficient 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 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 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.
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.
– 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.
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