Configure Spanning Tree
Step 1: Examine the default configuration of 802.1D STP.
On each switch, display the spanning tree table with the show spanning-tree command. Root selection
varies depending on the BID of each switch in your lab resulting in varying outputs.
S1#show spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 0019.068d.6980
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 0019.068d.6980
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1 Desg FWD 19 128.3 P2p
Fa0/2 Desg FWD 19 128.4 P2p
Fa0/3 Desg FWD 19 128.5 P2p
S2#show spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 0019.068d.6980
Cost 19
Port 1 (FastEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 001b.0c68.2080
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1 Root FWD 19 128.1 P2p
Fa0/2 Desg FWD 19 128.2 P2p
Fa0/6 Desg FWD 19 128.6 P2p
Fa0/11 Desg FWD 19 128.11 P2p
Fa0/18 Desg FWD 19 128.18 P2p
S3#show spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 0019.068d.6980
Cost 19
Port 1 (FastEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 001b.5303.1700
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1 Root FWD 19 128.1 P2p
Fa0/2 Altn BLK 19 128.2 P2p