Administrator Guide

34 Dell Campus Networking Interoperability with Cisco Catalyst 1.1 | version 1.1
2.8 Cisco Unidirectional Link Detection Interoperability
The Unidirectional Link Detection (UDLD) feature detects unidirectional links on physical ports. A
unidirectional link is a forwarding anomaly in a Layer 2 communication channel in which a bi-directional link
stops passing traffic in one direction. UDLD must be enabled on the both sides of the link in order to detect a
unidirectional link. The UDLD protocol operates by exchanging packets containing information about
neighboring devices. This feature is especially recommended when using fiber links.
2.8.1 Configuring UDLD — Dell N-Series
UDLD must first be enabled in global configuration mode and then on all participating physical interfaces. The
show udld command confirms general configuration and show udld te1/0/1 shows the UDLD state is in
Bidirectional (functioning) mode.
N3024#configure
N3024(config)#udld enable
N3024(config)#interface range te1/0/1-4
N3024 (config-if)#udld enable
N3024(config-if)#end
N3024#show udld
Admin Mode..................................... Enabled
Message Interval............................... 15
Timeout Interval............................... 5
N3024#show udld Tengigabitethernet 1/0/1
Interface Admin Mode UDLD Mode UDLD Status
--------- ---------- ----------- ---------------------------
Te1/0/1 Enabled Normal Bidirectional
2.8.2 Configuring UDLD — Cisco Catalyst
C6504#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
C6504(config)#udld enable
C6504(config)#end
C6504#show udld TenGigabitEthernet 2/1
Interface Te2/1
---
Port enable administrative configuration setting: Follows device default
Port enable operational state: Enabled
Current bidirectional state: Bidirectional
Current operational state: Advertisement - Single neighbor detected
Message interval: 15