21.2.2 IEEE 802.3 ah/UDLD Setting

To use IEEE 802.3ah/UDLD functionality, you must first enable IEEE 802.3ah/OAM functionality for the entire switch. As the factory default setting, IEEE 802.3ah/OAM functionality is enabled for the Switch (all ports are set to passive mode). Next, configure active mode with the UDLD parameter added for the ports on which you want to activate unidirectional link failure detection functionality.

Here, IEEE802.3ah/UDLD function is operated by gigabitethernet 1/0/1.

A unidirectional link failure is detected if the number of successive failures for checking the bidirectional link status resulting from a timeout of information sent from the link origination reaches the predetermined number. This predetermined number is the unidirectional link failure detection count. The bidirectional link status is checked once every second.

By changing the bidirectional link failure detection count, you can adjust the length of time between the actual occurrence of a unidirectional link failure and the time at which it is detected. If you decrease the count value, failures can be detected nearer the time of occurrence, but a greater risk of false detection. Normally, you do not change this setting.

The following is the approximate time from the occurrence of a unidirectional link failure and its detection (note that a maximum deviation of 10% is possible):

5 + unidirectional-link-failure-detection-count seconds