NEC INTELLIGENT L2 SWITCH N8406-022A - Manual (Page 86)

High availability 86
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 (20-24), one trunk group that contains only uplink ports,
or one LACP trunk group that contains only uplink ports. 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 and LACP trunk groups that contain only downlink ports. 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.
Configuration guidelines
This section provides important information about configuring UFD:
•
UFD is required only when uplink-path redundancy is not available on the blade switches.
•
Four Failure Detection pairs (one group of Links to Monitor and one group of Links to Disable) is supported
on each switch (all VLANs and Spanning Tree Groups).
•
An LtM can be any one of one uplink port, one trunk group of uplink ports, or one LACP trunk group of uplink
ports. Ports that are already members of a trunk group are not allowed to be assigned to an LtM.
•
A trunk group or a LACP trunk group configured as an LtM can contain multiple uplink ports (20-24), but no
downlink ports (1-16) or interconnect ports (17-18). An uplink port cannot be added to a trunk group if it
already belongs to an LtM.
•
An LtD can contain one or more ports, and/or one or more trunks, and/or one or more LACP trunks.
•
A trunk group or a LACP trunk group configured as an LtD can contain multiple downlink ports (1-16), but no
uplink ports (20-24) or interconnect ports (17-18).