This is good advice. As others have said, there's a few different methods you can use to track them down. - BPDU Guard (if they're running STP) - Looking for multiple MAC addresses on a single port. The latter will be the more accurate way of tracing, however you need to know your environment well enough to understand in what scenario's you might be seeing that behavior. You might see this from certain laptop docks performing MAC address passthrough, servers running virtualization, switchports connecting to AP's etc. If you have a lot of switches in your network, you might consider using the API to do the data gathering. You can output to CSV files and then do a lot of filtering in Excel.
... View more