We in one of the customer place using Cisco ME3400 switch. I am getting a problem that one of the fastethernet port (fa0/11) is getting error-disabled at very frequently. One third party unmanaged switch is connected in this port. each i time i have to login into the switch and have to do shutdown and no shutdown the port to enable this port. At the time of error-disabling the port it is giving a message that Loopback detected on fastethernet 0/13. Putting fatethernet 0/11 port in error-disabled state. I dont know exactly why it is happening. Please explain me that why it is happening and is there any way to disable this feature on cisco me3400 switch. Please help me as soon as possible.