We had an outage for one of our enterprise customer few days back. Upon recieving complaint we checked the network by capturing the traffic and found that there was ARP broadcast upto 40% of the total traffic captured and whole network was almost down that time. Finally we found a D-Link hub where an end connected back ethernet cable on the same hub caused loop in the network. We removed the cable and network came back to normal condition. My question is that how can we prevent such loop even if STP is running on the access layer switches where these type of hubs are connected becasue these hubs are not manageable so they don't send BPDUs. What could be the possible solution here to prevent such loops cause by end user ?
Another question is , if the campus network is flat means VLAN 1 is being used all over the campus than by creating multiple vlans can limit the scope of such loops to that VLAN only ?