Reference Guide

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UDLD

NOTE: This feature is only supported on the R1-2210 device.

This section describes how the Unidirectional Link Detection (UDLD)

feature.

It covers the following topics:

•Overview

• UDLD Global Settings

• UDLD Interface Settings

• UDLD Neighbors

Overview

Unidirectional Link Detection (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.

UDLD States and Modes

Under the UDLD protocol, ports are assigned the following states:

•

Detection

—System is attempting to determine whether the link is

bidirectional or unidirectional. This is a temporary state.