How to disable STP on a per port basis in Cisco Catalyst 2900XL - 2940 - 2950 - 2960 - 2970 - 3500XL - 3550 - 3560 - 3750 - 4000 - 4500 - 5000 - 5500 - 6000 - 6500 switches. By default, spanning tree runs on every port. The spanning tree feature cannot be turned off in switches on a per port basis. Although it is not recommended, you can turn off Spanning Tree Protocol (STP) on a per-VLAN basis, or globally on the switch. Use the no spanning-tree vlan vlan-id command in order to disable STP on a per virtual LAN (VLAN) basis. Also ensure that all switches and bridges in the VLAN have spanning tree disabled. You can't disable spanning tree on some switches and bridges in a VLAN and leave it enabled on other switches and bridges in the VLAN. If you do this, you can have unexpected results because switches and bridges with spanning tree enabled have incomplete information in regards to the physical topology of the network.
Note: Extreme care needs to be taken whenever you disable spanning tree because this creates Layer 2 loops within the network. Do not disable spanning tree in a VLAN, and make sure that there are no physical loops present in the VLAN. For further information refer to: Understanding and Configuring Spanning Tree Protocol (STP) on Catalyst Switches http://www.BradReese.Com