Enabling UDLD

UDLD is enabled on a per-port basis.

When at least one port is UDLD-enabled, the switch will forward out UDLD packets that arrive on non-UDLD-configured ports out of all other non-UDLD configured ports in the same vlan. That is, UDLD control packets will “pass through” a port that is not configured for UDLD. However, UDLD packets will be dropped on any blocked ports that are not configured for UDLD.

Enable UDLD on port a1

switch# interface al link-keepalive

Enter the appropriate port range to enable the feature on a trunk group

switch#interface al-a4 link-keepalive