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New Member

how long need a switch to detect a link down?

We want to migrate several Gigabitlinks over a DWDM Solution , the problem is.

If the DWDM switch over to the Backup Darkfiber the DWDM switch of the light for 50 ms to the Cisco Switch , the result is a link down on the Switchport.

so, how long can be no light on a Gbic till it goes down.

Cisco Employee

Re: how long need a switch to detect a link down?

50 ms switchover should not cause the gigabit link to go down. Do you actually see the system logging message indicating a link failover? Also, are you absolutely sure the DWDM is doing a fast trunk failover?

See this doc for more details:

New Member

Re: how long need a switch to detect a link down?

this link is really good, but we have 2950 Switches and the don´t know the debounce command.

The Command on IOS Switches is fist introduced in


Support for this command was introduced on the Supervisor Engine 720.


Support for this command on the Supervisor Engine 2 was extended to the 12.2 SX train.