Cisco Catalyst 3750-X Command Reference

2-971
Catalyst 3750-X and 3560-X Switch Command Reference
OL-29704-01
Chapter 2 Catalyst 3750-X and 3560-X Switch Cisco IOS Commands
udld
udld
Use the udld global configuration command on the switch stack or on a standalone switch to enable
aggressive or normal mode in the UniDirectional Link Detection (UDLD) and to set the configurable
message timer time. Use the no form of the command to disable aggressive or normal mode UDLD on
all fiber-optic ports.
udld {aggressive | enable | message time message-timer-interval}
no udld {aggressive | enable | message}
Syntax Description
Defaults UDLD is disabled on all interfaces.
The message timer is set at 15 seconds.
Command Modes Global configuration
Command History
Usage Guidelines UDLD supports two modes of operation: normal (the default) and aggressive. In normal mode, UDLD
detects unidirectional links due to misconnected interfaces on fiber-optic connections. In aggressive
mode, UDLD also detects unidirectional links due to one-way traffic on fiber-optic and twisted-pair links
and due to misconnected interfaces on fiber-optic links. For information about normal and aggressive
modes, see the “Understanding UDLD” section in the software configuration guide for this release.
If you change the message time between probe packets, you are making a trade-off between the detection
speed and the CPU load. By decreasing the time, you can make the detection-response faster but increase
the load on the CPU.
This command affects fiber-optic interfaces only. Use the udld interface configuration command to
enable UDLD on other interface types.
You can use these commands to reset an interface shut down by UDLD:
• The udld reset privileged EXEC command to reset all interfaces shut down by UDLD
• The shutdown and no shutdown interface configuration commands
• The no udld enable global configuration command followed by the udld {aggressive | enable}
global configuration command to re-enable UDLD globally
aggressive Enable UDLD in aggressive mode on all fiber-optic interfaces.
enable Enable UDLD in normal mode on all fiber-optic interfaces.
message time
message-timer-interval
Configure the period of time between UDLD probe messages on ports that
are in the advertisement phase and are determined to be bidirectional. The
range is 1 to 90 seconds. The default is 15 seconds.
Release Modification
12.2(53)SE2 This command was introduced.

Cisco Catalyst 3750-X Specifications

General

Brand	Cisco
Model	Catalyst 3750-X
Category	Switch
Language	English