Cisco Small Business 200 Series Administration Guide

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Cisco Small Business 200 Series Smart Switch Administration Guide 134
Port Management: Unidirectional Link
Detection
This section describes how the Unidirectional Link Detection (UDLD) feature.
It covers the following topics:
• UDLD Overview
• UDLD Operation
• Usage Guidelines
• Dependencies On Other Features
• Default Settings and Configuration
• Before You Start
• Common UDLD Tasks
• Configuring UDLD
UDLD Overview
UDLD is a Layer 2-protocol that enables devices connected through fiber-optic or twisted-pair Ethernet
cables to detect unidirectional links. A unidirectional link occurs whenever traffic from a neighboring device
is received by the local device, but traffic from the local device is not received by the neighbor.
The purpose of UDLD is to detect ports on which the neighbor does not receive traffic from the local device
(unidirectional link) and to shut down those ports.
All connected devices must support UDLD for the protocol to successfully detect unidirectional links. If only
the local device supports UDLD, it is not possible for the device to detect the status of the link. In this case,
the status of the link is set to undetermined. The user can configure whether ports in the undetermined state
are shut down or merely trigger notifications.

Cisco Small Business 200 Series Specifications

General

Brand	Cisco
Model	Small Business 200 Series
Category	Switch
Language	English