Command:

show spanning-tree

Mode:

Switch#


Syntax:

show spanning-tree [brief] | [summary] | [vlan stp-list] [interface interface-list] | [{begin | exclude | include} expression]


Syntax Description:

brief

Display a brief status of the spanning tree

summary

Display a summary of the spanning-tree states

vlan stp-list

(Optional) List of spanning-tree instances. Each spanning-tree instance is associated with a VLAN ID. Enter each VLAN ID separated by a space. Valid IDs are from 1 to 1001; do not enter leading zeroes.
Ranges are not supported.

interface interface-list

List of ports for which spanning-tree information is displayed. Enter each port separated by a space. Ranges are not supported.

| begin

(Optional) Display begins with the line that matches the specified expression

| exclude

(Optional) Display excludes lines that match the specified expression

| include

(Optional) Display includes lines that match the specified expression

expression

Expression in the output to use as a reference point


Command Description:

Use the show spanning-tree privileged EXEC command to display spanning-tree information for the specified spanning-tree instances.

If the variable stp-list is omitted, the command applies to the Spanning Tree Protocol (STP) instance associated with VLAN 1.

Expressions are case sensitive. For example, if you enter | exclude output, the lines that contain output are not displayed, but the lines that contain Output are displayed.


Examples:

The following is a sample of output from the show spanning-tree summary command:

Switch#show spanning-tree summary


UplinkFast is disabled

Name                 Blocking Listening Learning Forwarding STP Active
-------------------- -------- --------- -------- ---------- ----------
VLAN1                23       0         0        1          24
-------------------- -------- --------- -------- ---------- ----------
              1 VLAN 23       0         0        1          24

Switch#show spanning-tree brief

VLAN1
  Spanning tree enabled protocol IEEE
  ROOT ID    Priority 32768
             Address 0030.7172.66c4
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
VLAN1
  Spanning tree enabled protocol IEEE
  ROOT ID    Priority 32768
             Address 0030.7172.66c4
Port                           Designated
Name    Port ID Prio Cost Sts  Cost  Bridge ID      Port ID
------- ------- ---- ---- ---  ----  -------------- -------
Fa0/11  128.17  128  100  BLK  38    0404.0400.0001 128.17
Fa0/12  128.18  128  100  BLK  38    0404.0400.0001 128.18
Fa0/13  128.19  128  100  BLK  38    0404.0400.0001 128.19
Fa0/14  128.20  128  100  BLK  38    0404.0400.0001 128.20
Fa0/15  128.21  128  100  BLK  38    0404.0400.0001 128.21
Fa0/16  128.22  128  100  BLK  38    0404.0400.0001 128.22
Fa0/17  128.23  128  100  BLK  38    0404.0400.0001 128.23
Fa0/18  128.24  128  100  BLK  38    0404.0400.0001 128.24
Fa0/19  128.25  128  100  BLK  38    0404.0400.0001 128.25
Fa0/20  128.26  128  100  BLK  38    0404.0400.0001 128.26
Fa0/21  128.27  128  100  BLK  38    0404.0400.0001 128.27

Port                           Designated
Name    Port ID Prio Cost Sts  Cost  Bridge ID      Port ID
------- ------- ---- ---- ---  ----  -------------- -------
Fa0/22  128.28  128  100  BLK  38    0404.0400.0001 128.28
Fa0/23  128.29  128  100  BLK  38    0404.0400.0001 128.29
Fa0/24  128.30  128  100  BLK  38    0404.0400.0001 128.30 
Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

The following is a sample of output from the show spanning-tree command for VLAN 1:

Switch#show spanning-tree vlan 1


Spanning tree 1 is executing the IEEE compatible Spanning Tree protocol
  Bridge Identifier has priority 32768, address 00e0.1eb2.ddc0
  Configured hello time 2, max age 20, forward delay 15
  Current root has priority 32768, address 0010.0b3f.ac80
  Root port is 5, cost of root path is 10
  Topology change flag not set, detected flag not set, changes 1
  Times:  hold 1, topology change 35, notification 2
          hello 2, max age 20, forward delay 15
  Timers: hello 0, topology change 0, notification 0

Interface Fa0/1  in Spanning tree 1 is down
   Port path cost 100, Port priority 128
   Designated root has priority 32768, address 0010.0b3f.ac80
   Designated bridge has priority 32768, address 00e0.1eb2.ddc0
   Designated port is 1, path cost 10
   Timers: message age 0, forward delay 0, hold 0
   BPDU: sent 0, received 0
...

The following is a sample of output from the show spanning-tree interface command for port 3:


Switch#show spanning-tree interface fa0/3


Interface Fa0/3 (port 3) in Spanning tree 1 is down
   Port path cost 100, Port priority 128
   Designated root has priority 6000, address 0090.2bba.7a40
   Designated bridge has priority 32768, address 00e0.1e9f.4abf
   Designated port is 3, path cost 410
   Timers: message age 0, forward delay 0, hold 0
   BPDU: sent 0, received 0 

 


Misconceptions:
None

Related commands:
spanning-tree
spanning-tree forward-time
spanning-tree max-age
spanning-tree port-priority

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