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