27.9.2 Relation between VLAN debounce function and other functions

(1) Spanning tree

With Spanning Tree Protocols, the time required to change the Spanning Tree topology elapses before failure occurs on the port and it is switched to the alternate route. To prevent the VLAN interface from going down during this interval, set the VLAN interface down-determination time to a value greater than or equal to the time required to change the topology.

(2) Ring Protocol

When the Ring Protocol is used, the primary port is forwarded and the secondary port is blocked on the master node. If the VLAN Debounce functionality is not used and a failure occurs on the primary port, the VLAN interface goes down immediately, and goes back up once blocking is removed on the secondary port.

To prevent the VLAN from going down immediately in cases like this, set the time for which the VLAN interface's going down is delayed to a value greater than or equal to the protection time set by the health-check holdtime command.

(3) Other redundancy features

Even when redundancy functionality other than a Spanning Tree Protocol or Ring Protocol is used, when a VLAN repeatedly goes up and down in short intervals, the VLAN Debounce functionality can be used to suppress these events.