To view the spanning tree configuration and the interfaces that are participating in STP, use the showspanning-tree 0 command from EXEC privilege mode. If a physical interface is part of a port channel,only the port channel is listed in the command output.R2#show spanning-tree 0Executing IEEE compatible Spanning Tree ProtocolBridge Identifier has priority 32768, address 0001.e826.ddb7Configured hello time 2, max age 20, forward delay 15Current root has priority 32768, address 0001.e80d.2462Root Port is 289 (TenGigabitEthernet 2/1/1), cost of root path is 4Topology change flag not set, detected flag not setNumber of topology changes 3 last change occurred 0:16:11 agofrom TenGigabitEthernet 2/3/1Timers: hold 1, topology change 35hello 2, max age 20, forward delay 15Times: hello 0, topology change 0, notification 0, aging NormalPort 289 (TenGigabitEthernet 2/1/1) is ForwardingPort path cost 4, Port priority 8, Port Identifier 8.289Designated root has priority 32768, address 0001.e80d.2462Designated bridge has priority 32768, address 0001.e80d.2462Designated port id is 8.496, designated path cost 0Timers: message age 1, forward delay 0, hold 0Number of transitions to forwarding state 1BPDU: sent 21, received 486The port is not in the portfast modePort 290 (TenGigabitEthernet 2/2/1) is BlockingPort path cost 4, Port priority 8, Port Identifier 8.290--More--Timers: message age 1, forward delay 0, hold 0Number of transitions to forwarding state 1BPDU: sent 21, received 486The port is not in the portfast modeTo confirm that a port is participating in Spanning Tree, use the show spanning-tree 0 briefcommand from EXEC privilege mode.Dell#show spanning-tree 0 briefExecuting IEEE compatible Spanning Tree ProtocolRoot ID Priority 32768, Address 0001.e80d.2462We are the root of the spanning treeRoot Bridge hello time 2, max age 20, forward delay 15Bridge ID Priority 32768, Address 0001.e80d.2462Configured hello time 2, max age 20, forward delay 15Interface DesignatedName PortID Prio Cost Sts Cost Bridge ID PortID---------------- ------ ---- ---- --- ----- --------------------Te 1/1/1 8.496 8 4 DIS 0 32768 0001.e80d.2462 8.496Te 1/2/1 8.497 8 4 DIS 0 32768 0001.e80d.2462 8.497Te 1/3/1 8.513 8 4 FWD 0 32768 0001.e80d.2462 8.513Te 1/4/1 8.514 8 4 FWD 0 32768 0001.e80d.2462 8.514Dell#Adding an Interface to the Spanning Tree GroupTo add a Layer 2 interface to the spanning tree topology, use the following command.• Enable spanning tree on a Layer 2 interface.INTERFACE modeSpanning Tree Protocol (STP) 871
