Interfaces and Hardware Component Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

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Interfaces and Hardware Component Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

Configure UDLD

Updated: July 31, 2026

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This topic describes how to configure the Unidirectional Link Detection (UDLD) protocol on a physical ethernet interface, and optionally set the mode of operation, message time, and syslog message suppression for the interface.

UDLD is configured for each interface. The interface must be a physical ethernet interface.

Perform these steps to configure UDLD protocol on an interface.

Procedure

1.

Enter global configuration mode.

Example:

Router# configure
2.

Use the interface [GigabitEthernet | TenGigE] interface-path-id command. Enter interface configuration mode and specify the Ethernet interface name and notation rack/slot/module/port.

Example:

Router(config)# interface  TenGigE 0/1/0/0
Note

The example indicates an 8-port 10-Gigabit Ethernet interface in modular services card slot 1.
3.

Enable ethernet UDLD functionality and enters interface Ethernet UDLD configuration mode.

Example:

Router(config-if)# ethernet udld
4.

(Optional) Use the mode{ normal |aggressive} command to specify the mode of operation for UDLD. The options are normal and aggressive.

Example:

Router(config-if-udld)# mode normal
5.

(Optional) Use the message-time [7-90] command to specify the message time (in seconds) to use for the UDLD protocol. The value ranges from 7 to 90 seconds.

Example:

Router(config-if-udld)# message-time 70
6.

(Optional) Suppress the operational UDLD syslog messages.

Example:

Router(config-if-udld)# logging disable
7.

End the configuration session and exits to the EXEC mode.

Example:

Router(config-if-udld)# end