DELL S50V User Manual

Uplink Failure Detection (UFD) | 1087

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. This number is 
user-configurable and is calculated by the ratio of upstream port bandwidth to downstream port bandwidth 
in the same uplink-state group. This calculation ensures that there are 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 CPU usage.

Uplink Failure Detection on a switch can be used with network adapter teaming on a server (see 

 the switch/

router with UFD detects the uplink failure and automatically disables the associated downstream link port 
to the server. 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. 

Core
Network

Layer 3 Network

X

X

When an upstream  
port-channel link goes  
down ...

Server traffic is diverted over a backup link to upstream devices.

UFD brings down a  
downstream link in  
the same uplink- 
state group ...

Uplink-state groups:

Primary links:
Backup links: