Example:
To enable UDLD on port a1, enter:
switch(config)#interface al link-keepalive
To enable the feature on a trunk group, enter the appropriate port range. For example:
switch(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-UDLDconfigured 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 (CLI)
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 to 100 deciseconds, where 10 is 1 second, 11 is 1.1 seconds, and so on.
Example:
To change the packet interval to seven seconds, enter the following command at the global configuration level:
switch(config)# link-keepalive interval 70
Changing the keepalive retries (CLI)
By default, a port waits 5 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 to 10.
Example:
To change the maximum number of attempts to four, enter the following command at the global configuration
level:
switch(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-HPE 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:
switch(config)#interface link-keepalive vlan 22
Chapter 3 Port Status and Configuration
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