HP ProCurve Series 3400cl Release Notes page 93

Enabling UDLD. UDLD is enabled on a per port basis. For example, to enable UDLD on port a1,
enter:
ProCurve(config)#interface al link-keepalive
To enable the feature on a trunk group, enter the appropriate port range. For example:
ProCurve(config)#interface al-a4 link-keepalive
Note
When at least one port is UDLD-enabled, the switch will forward out UDLD packets that arrive on
non-UDLD-configured ports out of all other non-UDLD-configured ports in the same vlan. That is,
UDLD control packets will "pass through" a port that is not configured for UDLD. However, UDLD
packets will be dropped on any blocked ports that are not configured for UDLD.
Changing the Keepalive Interval. By default, ports enabled for UDLD send a link health-check
packet once every 5 seconds. You can change the interval to a value from 10 – 100 deciseconds,
where 10 is 1 second, 11 is 1.1 seconds, and so on. For example, to change the packet interval to
seven seconds, enter the following command at the global configuration level:
ProCurve(config)# link-keepalive interval 70
Changing the Keepalive Retries. By default, a port waits five seconds to receive a health-check
reply packet from the port at the other end of the link. If the port does not receive a reply, the port
tries four more times by sending up to four more health-check packets. If the port still does not
receive a reply after the maximum number of retries, the port goes down.
You can change the maximum number of keepalive attempts to a value from 3 – 10. For example, to
change the maximum number of attempts to 4, enter the following command at the global configu-
ration level:
ProCurve(config)# link-keepalive retries 4
Configuring UDLD for Tagged Ports. The default implementation of UDLD sends the UDLD
control packets untagged, even across tagged ports. If an untagged UDLD packet is received by a
non-ProCurve switch, that switch may reject the packet. To avoid such an occurrence, you can
configure ports to send out UDLD control packets that are tagged with a specified VLAN.
To enable ports to receive and send UDLD control packets tagged with a specific VLAN ID, enter a
command such as the following at the interface configuration level:
ProCurve(config)#interface l link-keepalive vlan 22
Enhancements
Release M.10.09 Enhancements
83