Dell PowerEdge FX2/FX2s - Manual (Page 206)

Figure 28. 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.
206 Uplink Failure Detection (UFD)