Quick Reference Guide

246 PowerConnect B-Series TI24X Configuration Guide
53-1002269-02
UDLD overview
9
Ports enabled for UDLD exchange proprietary health-check packets once every second (the
keepalive interval). If a port does not receive a health-check packet from the port at the other end
of the link within the keepalive interval, the port waits for two more intervals. If the port still does
not receive a health-check packet after waiting for three intervals, the port concludes that the link
has failed and takes the port down.
Configuration considerations
• This feature is supported only on Ethernet ports.
• To configure UDLD on a trunk group, you must enable and configure the feature on each port
of the group individually. Configuring UDLD on a trunk group primary port enables the feature
on that port only.
• When UDLD is enabled on a trunk port, trunk threshold is not supported.
• Dynamic trunking is not supported. If you want to configure a trunk group that contains ports
on which UDLD is enabled, you must remove the UDLD configuration from the ports. After you
create the trunk group, you can re-add the UDLD configuration.
• If MRP is also enabled on the device, Dell recommends that you set the MRP preforwarding
time slightly higher than the default of 300 ms; for example, to 400 or 500 ms. Refer to
“Changing the hello and preforwarding times” on page 213.
Enabling UDLD
To enable UDLD on a port, enter a command such as the following at the global CONFIG level of the
CLI.
PowerConnect(config)#link-keepalive ethernet 1
To enable the feature on a trunk group, enter commands such as the following.
PowerConnect(config)#link-keepalive ethernet 1 ethernet 2
PowerConnect(config)#link-keepalive ethernet 3 ethernet 4
Syntax: [no] link-keepalive ethernet [portnum] ethernet [portnum]
These commands enable UDLD on ports 1 – 4.
PowerConnect(config)#link-keepalive ethernet 1 to 5 ethernet 7
Syntax: [no] link-keepalive ethernet [portlist]
Changing the Keepalive interval
By default, ports enabled for UDLD send a link health-check packet once every 500 ms. You can
change the interval to a value from 1 – 60, where 1 is 100 ms, 2 is 200 ms, and so on. To change
the interval, enter a command such as the following.
PowerConnect(config)#link-keepalive interval 3
Syntax: [no] link-keepalive interval <num>
The <num> parameter specifies how often the ports send a UDLD packet. You can specify from 1
– 60, in 100 ms increments. The default is 5 (500 ms).