Link Debounce

Table 1. Link Debounce for WAN Links
Feature	Product	Release introduced
Link Debounce	5320 Series	Fabric Engine 8.6
	5420 Series	VOSS 8.5
	5520 Series	VOSS 8.5
	5720 Series	Fabric Engine 8.7
	7520 Series	Fabric Engine 8.10
	7720 Series	Fabric Engine 8.10
	VSP 4900 Series	VOSS 8.4.2
	VSP 7400 Series	VOSS 8.4.2

In a WAN environment, when a carrier-side link failure occurs, switchover on the carrier side can take a few hundred milliseconds. During that time, a lag in the sending and receiving of packets can occur. Use Link Debounce to hold the connection path until the switchover is complete. You can configure Link Debounce on each port.

Link Debounce protects the upper layers from unnecessary state changes by delaying the change of a port link state when the following situations occur:

There are frequent flaps in a short interval at the physical layer in the case of Fiber WAN services.

There is a delay in switching from the working path to the protected path in the case of Carrier Wave WAN services.

Link Debounce works only on Layer 1 protocol applications. Layer 2 / Layer 3 protocols make decisions based on how they receive packets. For example, STP makes the decision according to the lack of traffic and port up condition; OSPF and IS-IS can still fail adjacencies.

ExtremeCloud SD-WAN

Auto-sense automatically configures Link Debounce on the switch port that connects to SD-WAN Appliance. This configuration enables the switch that connects to the appliance LAN1 port to keep using its FE VXLAN tunnels over MPLS transport, even if SD-WAN Appliance is down, Layer 3 WAN Internet ports are lost, and the appliance is in Bypass mode.

If you do not configure a timer value and the port connects to SD-WAN Appliance, Auto-sense configures a value of 8000 milliseconds. Auto-sense does not overwrite a configured timer value.