Spanning-tree Loop Troubleshooting and SafeGuards Configuring Root Guard & Loop Guard BPDU Guard, BPDU Filter, Root Guard, Loop Guard & UDLD What Is the Difference Between STP BPDU Guard and STP Root Guard? Of course there are more technical and in depth articles at sites such as Cisco.com ( here , here , here , here etc.) and others. Google is your friend :-)
Links, commands and settings I someday probably won't find again