#T-Shoot Spanning Tree useful command
SW2#show spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 4097
Address 0017.956e.fa00
Cost 19
Port 24 (FastEthernet0/24)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 8193 (priority 8192 sys-id-ext 1)
Address 0013.c426.0b00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/23 Desg FWD 19 128.23 P2p
Fa0/24 Root FWD 19 128.24 P2p
SW2#show spanning-tree bridge
Hello Max Fwd
Vlan Bridge ID Time Age Dly Protocol
---------------- --------------------------------- ----- --- --- --------
VLAN0001 8193 ( 8192, 1) 0013.c426.0b00 2 20 15 ieee
SW2#show spanning-tree bridge ?
address Mac address of this bridge
detail Detailed of the status and configuration
forward-time Forward delay interval
hello-time Hello time
id Spanning tree bridge identifier
max-age Max age
priority Bridge priority of this bridge
protocol Spanning tree protocol
| Output modifiers
<cr>
SW2#show spanning-tree bridge priority
VLAN0001 8193
SW2#show spanning-tree bridge address
VLAN0001 0013.c426.0b00
SW2#show spanning-tree bridge protocol
VLAN0001 ieee
SW2#show spanning-tree bridge hello-time
VLAN0001 2
! See if everyone agrees on the root
SW1#show spanning-tree vlan 1 root
Root Hello Max Fwd
Vlan Root ID Cost Time Age Dly Root Port
---------------- -------------------- --------- ----- --- --- ------------
VLAN0001 4097 0017.956e.fa00 0 2 20 15
! This switch is Root
SW2#show spanning-tree vlan 1 root
Root Hello Max Fwd
Vlan Root ID Cost Time Age Dly Root Port
---------------- -------------------- --------- ----- --- --- ------------
VLAN0001 4097 0017.956e.fa00 19 2 20 15 Fa0/24
! SW2 can reach to the Root via Fa0/23 (Cost 19)
#Root Port Election
! If Cost, Bridge ID,port priority are same, the best port will be with lower Port # we recive.
SW3#show spanning-tree vlan 1 detail | begin Port 24
Port 24 (FastEthernet0/24) of VLAN0001 is blocking
Port path cost 19, Port priority 128, Port Identifier 128.24.
Designated root has priority 4097, address 0017.956e.fa00
Designated bridge has priority 8193, address 0013.c426.0b00
Designated port id is 128.23, designated path cost 19
Timers: message age 3, forward delay 0, hold 0
Number of transitions to forwarding state: 1
Link type is point-to-point by default
BPDU: sent 4, received 12208
! Check Designated port id
Port path cost = 19
Port priority = 128
Designated port id is 128.23
! 23 is Port number of remote switch. (Fa0/23)
SW2#show spanning-tree vlan 1 summary
Switch is in pvst mode
Root bridge for VLAN0001 is 4097.0017.956e.fa00.
Extended system ID is enabled
Portfast Default is disabled
PortFast BPDU Guard Default is disabled
Portfast BPDU Filter Default is disabled
Loopguard Default is disabled
EtherChannel misconfig guard is enabled
UplinkFast is disabled
BackboneFast is disabled
Configured Pathcost method used is short
Name Blocking Listening Learning Forwarding STP Active
---------------------- -------- --------- -------- ---------- ----------
VLAN0001 0 0 0 2 2
