第一种方法 依靠三层设备的物理接口进行转发

PC0:
IP: 192.168.2.2 子网掩码: 255.255.255.0 默认网关: 192.168.2.1
PC1:
IP: 192.168.3.2 子网掩码: 255.255.255.0 默认网关: 192.168.3.1
Router0:
Fa0/0: IP:192.168.3.1/24 Fa0/1: IP:192.168.2.1/24
Switch0:
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
2 vlan2 active Fa0/2, Fa0/4
3 vlan3 active Fa0/1, Fa0/3
Switch0:
> Switch0>en
> Switch0#conf t
> Switch0(config)#vlan 2
> Switch0(config-vlan)#name vlan2
> Switch0(config-vlan)#vlan 3
> Switch0(config-vlan)#name vlan3
> Switch0(config-vlan)#ex
>
> Switch0(config)#int range fa0/2, fa0/4
> Switch0(config-if-range)#switchport mode access
> Switch0(config-if-range)#switchport access vlan 2
> Switch0(config-if-range)#ex
>
> Switch0(config)#int range fa0/1, fa0/3