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Catalyst4500 Series SwitchCiscoIOS Command Reference—Release 12.2(18)EW
78-16201-01
Chapter2Cisco IOS Commands for the Catalyst 4500 Series Switches
udld (interface configuration mode)
udld (interface configuration mode)
To enable UDLD on an individual interface or to prevent a fiber interface from being enabled by the udld
(global configuration mode) command, use the udld command. To return to the udld (global
configuration mode) command setting, or if the port is a nonfiber port to disable UDLD, use the no
form of this command.
udld {enable | aggressive | disable}
no udld {enable | aggressive | disable}
Syntax Description
Defaults The fiber interfaces are enabled per the state of the global udld (enable or aggressive) command, and
the nonfiber interfaces are enabled with UDLD disabled.
Command Modes Interface configuration
Command History
Usage Guidelines If you enable aggressive mode, once all the neighbors of a port have aged out either in the advertisement
or in the detection phase, UDLD restarts the linkup sequence to try to resynchronize with any potentially
out-of-sync neighbor and shuts down the port if the message train from the link is still undetermined.
Use the no udld enable command on fiber ports to return control of UDLD to the global udld enable
command or to disable UDLD on nonfiber ports.
Use the udld aggressive command on fiber ports to override the setting of the global udld (enable or
aggressive) command. Use the no form on fiber ports to remove this setting, return control of UDLD enabling
back to the global udld command or to disable UDLD on nonfiber ports.
The disable keyword is supported on fiber ports only. Use the no form of this command to remove this
setting and return control of UDLD to the udld (global configuration mode) command.
If the port changes from fiber to nonfiber or vice versa, all configurations will be maintained because of
a change of module or a GBIC change detected by the platform software.
Examples This example shows how to cause any port interface to enable UDLD, despite the current global udld
(global configuration mode) setting:
Switch (config-if)# udld enable
Switch (config-if)#
enable Enables UDLD on this interface.
aggressive Enables UDLD in aggressive mode on this interface.
disable Disables UDLD on this interface.
Release Modification
12.1(8a)EW Support for this command was introduced on the Catalyst 4500 series switch.
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