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To view the spanning tree configuration and the interfaces that are participating in STP, use the show
spanning-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 0
Executing IEEE compatible Spanning Tree Protocol
Bridge Identifier has priority 32768, address 0001.e826.ddb7
Configured hello time 2, max age 20, forward delay 15
Current root has priority 32768, address 0001.e80d.2462
Root Port is 289 (TenGigabitEthernet 2/1), cost of root path is 4
Topology change flag not set, detected flag not set
Number of topology changes 3 last change occurred 0:16:11 ago
from TenGigabitEthernet 2/3
Timers: hold 1, topology change 35
hello 2, max age 20, forward delay 15
Times: hello 0, topology change 0, notification 0, aging Normal
Port 289 (TenGigabitEthernet 2/1) is Forwarding
Port path cost 4, Port priority 8, Port Identifier 8.289
Designated root has priority 32768, address 0001.e80d.2462
Designated bridge has priority 32768, address 0001.e80d.2462
Designated port id is 8.496, designated path cost 0
Timers: message age 1, forward delay 0, hold 0
Number of transitions to forwarding state 1
BPDU: sent 21, received 486
The port is not in the portfast mode
Port 290 (TenGigabitEthernet 2/2) is Blocking
Port path cost 4, Port priority 8, Port Identifier 8.290
--More--
Timers: message age 1, forward delay 0, hold 0
Number of transitions to forwarding state 1
BPDU: sent 21, received 486
The port is not in the portfast mode
To confirm that a port is participating in Spanning Tree, use the show spanning-tree 0 brief
command from EXEC privilege mode.
Dell#show spanning-tree 0 brief
Executing IEEE compatible Spanning Tree Protocol
Root ID Priority 32768, Address 0001.e80d.2462
We are the root of the spanning tree
Root Bridge hello time 2, max age 20, forward delay 15
Bridge ID Priority 32768, Address 0001.e80d.2462
Configured hello time 2, max age 20, forward delay 15
Interface Designated
Name PortID Prio Cost Sts Cost Bridge ID PortID
-------------- ------ ---- ---- --- ----- --------------------
Te 1/1 8.496 8 4 DIS 0 32768 0001.e80d.2462 8.496
Te 1/2 8.497 8 4 DIS 0 32768 0001.e80d.2462 8.497
Te 1/3 8.513 8 4 FWD 0 32768 0001.e80d.2462 8.513
Te 1/4 8.514 8 4 FWD 0 32768 0001.e80d.2462 8.514
Dell#
Adding an Interface to the Spanning Tree Group
To add a Layer 2 interface to the spanning tree topology, use the following command.
• Enable spanning tree on a Layer 2 interface.
INTERFACE mode
Spanning Tree Protocol (STP)
873