27.9.1 Overview

A VLAN interface goes up when communication is possible for the VLAN, and goes down when the VLAN port goes down, or a Spanning Tree Protocol or other functionality causes blocking and prevents communication.

VLAN debounce function delays the up and down of VLAN interfaces, and reduces network topology changes, operational messaging, SNMP notification, and so on.

When failure occurs for redundant configurations using a Spanning Tree Protocol or Ring Protocol on a Layer 2, the time required to switch routes is less than a normal Layer 3 topology change. The VLAN Debounce functionality keeps the VLAN interface from going down for the time that it takes to switch routes on the layer, which preserves communication availability without changing the Layer 3 topology.

When a redundant configuration is used for Layer 3, and recovery is performed after failure occurs on the master, the VLAN Debounce functionality can be used to delay when the VLAN interface goes up, which prevents both nodes from running as the master.