Install Guide

Figure 129. 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.
● 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. 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.
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Uplink Failure Detection (UFD)