lo time period. If the port does not receive a BPDU for a specified period, the port moves into the blocking state and is not used in the root port calculation. Once that port receives a BPDU, it resumes the normal spanning tree transitions. Here's what you need to remember: BA is always on unless globally disabled, and BPDUs are sent out every operational networking port when it's enabled. More to the point, if you don't manage BA properly, it will break your network. While that's true of spanning tree as well, we've all become used to how STP operates. BA changes the rules a bit. BA is only supported by Rapid PVST+ and MST. This is important, because for BA to work properly, it must be enabled and configured on both sides of a link. If you plug your Nexus 5K into a 2960 that's running PVST, BA may disable the link to the 2960. With Nexus, spanning tree ports are identified as normal, host, or network. A host port is analogous to spanning-tree portfast in IOS. A network port is a port that is not connected to a host but is connected to another BA-capable switch. While you might be tempted to make all your trunk ports spanning tree network ports, be careful. I had a client for whom we connected a Nexus 5K to a 6509. The 6509 supported bridge assurance, but we weren't paying attention when we configured the interswitch link. The Nexus side got configured for spanning tree port type network (it was a network port, after all), but what we didn't count on was the 6509 running PVST. As a result, the Nexus blocked many of our VLANs. Changing the trunk port to spanning tree type normal solved the problem. Common Spanning Tree Problems Designing to Prevent Spanning Tree Problems Proper design can help minimize spanning tree problems. One of the simplest ways to help keep trouble to a minimum is to document and know your network. If you have to figure out how your network operates when there's a problem, the problem may last longer than your job. Use Routing Instead of Switching for Redundancy The saying used to be, "Swit