There are several methods to troubleshoot a switching loop. It is possible that not all switches within your network have spanning-tree enabled thus leaving your network exposed to broadcast storms caused by these loops. Spanning-tree troubleshooting commands may be able to help you out to a certain degree. The command "show span" gives a good summary of what state each port is in. The commands "debug spanning-tree topology" and "debug spanning-tree events" will give you an idea if the switch is noticing any topology changes forcing spanning-tree to recalculate. The important thing to take from these commands is that spanning-tree is allowing traffic to flow through your switching network as you want it to. More details in configuring spanning-tree can be found in this document: https://supportforums.adtran.com/docs/DOC-1661
Beyond that, I find the "show arp" and "show mac address-table" commands helpful. What I am looking for in these tables are duplicate entries, which points to the fact that these entries were learned twice and from a different source. These commands allow me to trace these duplicate entries through the switch network and usually lead to the culprit device.
As far as preventing these events from hindering your network, all NetVanta switches have a feature called storm control available within them. Storm control allows the switch to monitor input and output rates on a port. If the traffic on the port exceeds a certain amount, the port begins to drop excess traffic OR, depending on the switch available, shuts the port down to prevent further network instability until traffic falls back below the threshold. The following thread on storm control provides more details on each switch's capabilities and how to go about configuring it: https://supportforums.adtran.com/message/2376
Please do not hesitate to let us know if you have any further questions.
Very helpful, Noor. Thanks for being so thorough! I'll look over the spanning-tree document.
Any guidelines about setting the storm control thresholds?