9 128.13 Fao/14 Altn BLK 19 128.14 Fao/15 Altn BLK 19 128.15 Fao/20 Root FWD 19 128.20 Fao/23 Desg FWD 19 128.23 [-text removed- The bolded text shows the priority and MAC address of the root bridge, as well as which port the switch is using to get there (this is the root port). This is very useful information when you're trying to figure out where the root bridge is on a network. By running this command on every switch in the network, you should be able to map your connections and figure out which switch is the root. Here is the output from the show spanning-tree command from a Nexus 7000 that is operating as the STP root: NX-7K-1-Cozy# sho spanning VLAN0001 Spanning tree enabled protocol rstp Root ID Priority 32769 Address 0026.9807.95c2 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address 0026.9807.95c2 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Interface Role Sts Cost Prio.Nbr Type Desg FWD 1 128.4096 (vPC peer-link) Network P2p Desg FWD 1 128.4105 (vPC) P2p [-text removed- ] Switch-specific information is located below the root information, and below the local switch information is information specific to each port on the switch that is actively participating in spanning tree. This information will be repeated for every VLAN. In CatOS, the equivalent command is show spantree. The command produces very similar information, with a slightly different layout: Chapter 8: Spanning Tree Catos-6509 (enable) sho spantree VLAN 1 Spanning tree mode RAPID-PVST+ Spanning tree type Spanning tree enabled Designated Root 00-00-00-00-00-00 Designated Root Priority Designated Root Cost Designated Root Port Root Max Age 0 sec Hello Time 0 sec Forward Delay 0 sec Bridge ID MAC ADDR 00-00-00-00-00-00 Bridge ID Priority 32768 Bridge Max Age 20 sec Hello Time 2 sec Forward Delay 15 sec State Role Cost Prio Type not-connected - not-connected - not-connected - not-connected - [-text removed- Notice that the designated root MAC address is