HP 2910AL - Manual (Page 246)

Port Status and Configuration
Uni-Directional Link Detection (UDLD)
N o t e 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 configuration 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
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