By identifying where issues can occur in a Spanning Tree environment, and
defining why these issues occur can make it easier to isolate the problems when
they occur. Enhancements have been made to the STP protocol to help reduce the
likelihood of anomalous STP conditions if they are implemented. Forwarding
Loops and Black Holes are conditions that can result from improper Spanning
Tree operation. These conditions can be detected and prevented through the
execution of specific troubleshooting and configuration commands. Two major
enhancements have been made to original 802.1D specifications for Spanning
Tree. Rapid Spanning Tree, 802.1w, provides a faster and more resilient means
of adapting to topology change in a switched environment. Multiple Spanning
Tree provides an alternative to Per VLAN and Common Spanning Tree by requiring
only a minimal number of STP instances in a switched environment.