这两台接入层交换机上的配置比较简单，就是启用了一些PVST+特性，然后配置各中继链路允许对应的VLAN通信通过。
Access 1交换机的原始PVST+配置（可通过show running-config特权模式命令查看）：
Access 1#show running-config
Building configuration...
!
spanning-tree mode pvst
spanning-tree portfast bpduguard default
spanning-tree extend system-id
spanning-tree uplinkfast
spanning-tree backbonefast
!
vlan 10,20
!
interface FastEthernet0/1
switchport trunk encapsulation dot1q
switchport mode trunk
switchport trunk allowed vlan 10,20
!
interface FastEthernet0/2
switchport trunk encapsulation dot1q
switchport mode trunk
switchport trunk allowed vlan 10,20
!
end
Access 2交换机的原始PVST+配置（注意，这是一台CatOS操作系统的交换机，可通过show config all特权模式命令查看）：
Access 2> (enable)show config all
#mac address reduction
set spantree macreduction enable
!
#stp mode
set spantree mode pvst+
!
#uplinkfast groups
set spantree uplinkfast enable rate 15 all-protocols off
!
#backbonefast
set spantree backbonefast enable
!
#vlan parameters
set spantree priority 49152 1
set spantree priority 49152 30
set spantree priority 49152 40
!
#vlan(defaults)
set spantree enable 1,30,40
set spantree fwddelay 15 1,30,40
set spantree hello 2 1,30,40
set spantree maxage 20 1,30,40
!
#vtp
set vlan 1,30,40
!
#module 3 : 48-port 10/100BaseTX Ethernet
set trunk 3/3 on dot1q 30,40
set trunk 3/4 on dot1q 30,40
!
end