All of us have worked with, or at least heard about, Spanning Tree Protocol (STP). The reason I call this recipe Analyzing spanning tree problems is that there are three major versions of it, as follows:

• STP: This is an IEEE 802.1D standard from 1998, called 802.1D-1998
• Rapid Spanning Tree Protocol (RSTP): This is an IEEE 802.1W standard from 2001, later added to 802.1D, called 802.1D-2004
• Multiple Spanning Tree (MST): This was originally defined in IEEE 802.1S and later merged into IEEE 802.1Q

There are also some proprietary versions from Cisco and other vendors. In this recipe, we will focus on the standard versions and learn how to troubleshoot problems that might occur during STP/RSTP/MST operations.