Can a Layer 2 loop happen in your campus network? You may say, I am running Spanning Tree Protocol (STP), and it is designed to maintain a loop-free layer 2 topology. This is true, but despite the use of STP, some scenarios such as wiring mistakes, unauthorized use of devices, misconfigured hosts, or switch configuration errors can lead to spanning tree loops. In the article Protecting a Cisco Catalyst 6500 Switch Against Layer 2 Loops I present the steps I followed to develop a solution to alleviate the impact of a Layer 2 loop on a Catalyst 6500 switch.
I hope this may help!