Ports on Cisco Catalyst switches send periodic frames that uniquely identify the device and the port they are sent from. These frames are called loop detection frames. If a port receives a loop detection frame it has sent out itself then the frame must have indeed returned to its origin port via a loop. In such a case, the port will be err-disabled.
I suppose that this is what is happening to you - a loop detection frame is received by a port that has originated it. The question is, why does this happen. One of possible causes is indeed a loop in your network created by multiple connections between your switches and/or hubs. Another possibility is that you have a device connected on your network that for some inexplicable reason sends out the traffic that it just received (this is what can be called a mirroring) - I can imagine a Linux or Windows machine with multiple NICs in bridging/teaming mode doing this, for example. And yet another option is a forgotten SPAN session running on your switches that returns the captured traffic back to the network for whatever reasons.
I am sorry I cannot help you more precisely but there are frankly many possible ways for this error to happen. The primary principle stands, though - a port receives back its own loop detection frame. The detective work is now necessary why the frame indeed loops back.
This is actually a pretty cool feature, i didn't even know it existed until I was looking for a solution to advertise a subnet (prefix in BGP talk), only if a certain condition existed. This is exactly what conditional advertisements does
j ai une question j ai achete un routeur cisco 887VA-k9 , je le configuré avec la configuration ci- dessous
si je le lier avec mon pc portable sur l un de ses ports directement ça marche toute est bien ( la connexion internet + m...
Attached policy provides CLI access to the Cisco 4G router over text messaging. Two files are in the attached .tar file:
2. PDF with instructions on how to load and use the .tcl file.