AR1是合法路由，AR2是非法路由

dhcp en
dhcp snooping en      //全局开启dhcp snooping
port-group group-member e0/0/1 to e0/0/12
dhcp snooping en      //配置1-12端口开启dhcp snooping
q
int e0/0/1
dhcp snooping trusted   //配置e0/0/1口为信任dhcp端口