Let me start by saying that spanning tree is a Good Thing. It saves you from loops, which will completely shut down a network. But it has to be configured properly to work properly. I can’t count the number of times I’ve had a client call me, desperate with a terribly broken network, and I’ve responded, “Sounds like a spanning tree problem.” There are many ways things can go wrong with spanning tree . In this article I’ve collected a few of the recurring themes. Read the article over at auvik over here .