配置扩展ACL规则
access-list 150 permit ip any 172.23.0.0 0.0.255.255
access-list 150 permit tcp any 172.23.0.0 0.0.255.255 eq telnet
access-list 150 permit icmp any 172.23.0.0 0.0.255.255
access-list 150 permit tcp any 172.23.0.0 0.0.255.255 eq www
access-list 150 permit tcp any 172.23.0.0 0.0.255.255
access-list 150 permit udp any 172.23.0.0 0.0.255.255
access-list 150 permit udp any any eq bootpc
access-list 150 permit udp any any eq bootps    

最后两行保证了端口所接电脑能从dhcp server获得ip地址
在端口应用策略
interface FastEthernet0/2
 ip access-group 150 in