HP 445946-001 - Manual (Page 168)

High availability
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Figure 24 Uplink Failure Detection for switches
Failure Detection Pair
To use UFD, you must configure a Failure Detection Pair and then turn UFD on. A Failure Detection Pair
consists of the following groups of ports:
• Link to Monitor (LtM)
The Link to Monitor group consists of one uplink port (18-21), or one trunk group that contains only
uplink ports. The trunk group can be a Link Aggregation Control Protocol trunk. The switch monitors
the LtM for link failure.
• Link to Disable (LtD)
The Link to Disable group consists of one or more downlink ports (1-16) and trunk groups that
contain only downlink ports. The trunk groups can be Link Aggregation Control Protocol trunks.
When the switch detects a link failure on the LtM, it automatically disables all ports in the LtD.
When the LtM returns to service, the switch automatically enables all ports in the LtD.
Spanning Tree Protocol with UFD
If Spanning Tree Protocol (STP) is enabled on ports in the LtM, then the switch monitors the STP state and
the link status on ports in the LtM. The switch automatically disables the ports in the LtD when it detects a
link failure or STP Blocking state.
When the switch determines that ports in the LtM are in STP Forwarding State, then it automatically
enables the ports in the LtD, to fall back to normal operation.