Explanation/Reference:
* The following commands allow you to configure UDLD via the CLI.
Syntax: [no] interface <port-list> link-keepalive
Enables UDLD on a port or range of ports
* Ports enabled for UDLD exchange health-check packets once every five seconds (the link-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 four more intervals. If the port still does not receive a healthcheck packet after waiting for five intervals, the port concludes that the link has failed and blocks the UDLD- enabled port.
Reference: Port Status and Basic Configuration
ftp://ftp.hp.com/pub/networking/software/2900yl-MCG-0207-T_12_XX-Chap10-PrtStat-BasicCfg.pdf