Udld - Cisco Catalyst 2960-X Command Reference Manual

Layer 2 Commands

udld

To enable aggressive or normal mode in the UniDirectional Link Detection (UDLD) and to set the configurable
message timer time, use the udld command in global configuration mode. To disable aggressive or normal
mode UDLD on all fiber-optic ports, use the no form of the command.
udld {aggressive| enable| message time message-timer-interval}
no udld {aggressive| enable| message}
Syntax Description
aggressive
enable
message time
message-timer-interval
Command Default
UDLD is disabled on all interfaces.
The message timer is set at 15 seconds.
Command Modes
Global configuration
Command History
Release
Cisco IOS 15.0(2)EX
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
Catalyst 2960-X Switch Layer 2 Configuration GuideCatalyst 2960-XR Switch Layer 2 Configuration Guide.
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.
OL-29043 -01
Enables UDLD in aggressive mode on all fiber-optic interfaces.
Enables UDLD in normal mode on all fiber-optic interfaces.
Configures 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.
Modification
This command was introduced.
Catalyst 2960-X Switch Layer 2 Command Reference, Cisco IOS Release 15.0(2)EX
udld
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