Quick Reference Guide

PowerConnect B-Series TI24X Configuration Guide 245
53-1002269-02
Chapter
9
Configuring Uni-Directional Link Detection (UDLD) and
Protected Link Groups
UDLD overview
Uni-Directional Link Detection (UDLD) monitors a link between two devices and brings the ports on
both ends of the link down if the link goes down at any point between the two devices. This feature
is useful for links that are individual ports and for trunk links. Figure 53 shows an example.
FIGURE 53 UDLD example
Normally, a device load balances traffic across the ports in a trunk group. In this example, each
device load balances traffic across two ports. Without the UDLD feature, a link failure on a link that
is not directly attached to one of the devices is undetected by the devices. As a result, the devices
continue to send traffic on the ports connected to the failed link.
When UDLD is enabled on the trunk ports on each device, the devices detect the failed link, disable
the ports connected to the failed link, and use the remaining ports in the trunk group to forward the
traffic.
X
Without link keepalive, the ports remain
enabled. Traffic continues to be load balanced to the
ports connected to the failed link.
When link keepalive is enabled, the feature
brings down the ports connected
to the failed link.
Switch Switch