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Alteon OS Application Guide
Chapter 13: High Availability
21942C4911, January 2007
Setting the Failover Limit
The failover limit lets you specify the minimum number of operational links required
within each trigger before the trigger initiates a failover event. For example, if the limit is two
(/cfg/l2/failovr/trigger x/limit 2), a failover event occurs when the number
of operational links in the trigger is two or fewer. When you set the limit to zero, the switch
triggers a failover event only when no links in the trigger are operational.
L2 Failover with Other Features
L2 Failover works together with Link Aggregation Control Protocol (LACP) and with
Spanning Tree Protocol (STP), as described below.
LACP
Link Aggregation Control Protocol allows the switch to form dynamic trunks.
You can use the admin key to add LACP trunks to a failover trigger. When you add an admin
key to a trigger (/cfg/failovr/trigger x/amon/addkey), any LACP trunk with
that admin key becomes a member of the trigger.
Spanning Tree Protocol
If Spanning Tree Protocol (STP) is enabled on the ports in a failover trigger, the switch moni-
tors the port STP state rather than the link state. A port failure results when STP is not in a For-
warding state (that is, Listening, Learning, Blocking, or No Link). The switch automatically
disables the appropriate internal ports, based on the VLAN monitor.
When the switch determines that ports in the trigger are in STP Forwarding state, then it auto-
matically enables the appropriate internal ports, based on the VLAN monitor. The switch fails
back to normal operation.