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Link-flap error detected on Cisco 3750

I have a 3750 switch that bridges our corporate office to our Ethernet Network.

1- The port that bridges corporate office to the Ethernet Network is a L3 interface.

2- The port went into err-disable state, their was no recovery so the interface stayed down

3- The messages was "%PM-4-ERR_DISABLE: link-flap error detected on FA1/0/1" on the Cisco 3750

4- The port was receiving input errors and CRC's, counters incrementing fast

5- During a maintenace that was unrelated to the Cisco 3750, port Fa1/0/1flapped once then went into err-disable state

6- No other alarms in "show log" of the 3750

7- Can a loop on the network cause a port to flap once and place the port in err-disable state with the "link-flap error" alarm?

8- My question is general, need to know if this is possible.  I know what caused a loop and I resolved it.  Everything normalized but curious, did the 3750 mean to send an alarm stating "%PM-4-ERR_DISABLE: loopback error detected on"?



Re: Link-flap error detected on Cisco 3750


If you give loop on your fa1/0/1 then the keepalive message sent back and port goes in error diable state with log message as

"loopback error detected on fa1/0/1"

But if there is a link flap with flap of more than 5 in 10 seconds then it will go to error diable state with below message

"link-flap error detected on fa1/0/1"

I hope this is sufficient to understand how link flap cause port to move to error diable state.



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