A10E/A28E/A28F Configuration Guide
SwitchB(config)#spanning-tree enable
SwitchB(config)#spanning-tree mode stp
Configure Switch C.
Alpha-A28E#hostname SwitchC
SwitchC#config
SwitchC(config)#spanning-tree enable
SwitchC(config)#spanning-tree mode stp
Step 2 Configure interface mode on three switches.
Configure Switch A.
SwitchA(config)#interface port 1
SwitchA(config-port)#switchport mode trunk
SwitchA(config-port)#exit
SwitchA(config)#interface port 2
SwitchA(config-port)#switchport mode trunk
SwitchA(config-port)#exit
Configure Switch B.
SwitchB(config)#interface port 1
SwitchB(config-port)#switchport mode trunk
SwitchB(config-port)#exit
SwitchB(config)#interface port 2
SwitchB(config-port)#switchport mode trunk
SwitchB(config-port)#exit
Configure Switch C.
SwitchC(config)#interface port 1
SwitchC(config-port)#switchport mode trunk
SwitchC(config-port)#exit
SwitchC(config)#interface port 2
SwitchC(config-port)#switchport mode trunk
SwitchC(config-port)#exit
Step 3 Configure priority of spanning tree and interface path cost.
Configure Switch A.