静态NAT：
Router(config-if)#ip nat { outside | inside } 定义外部接口和内部接口。
Router(config)#ip nat {inside | outside }source static source_address translate_address
定义源地址翻译。
router1(config)# ip nat inside source static 160.10.1.2 169.10.1.2
router1(config)# interface ethernet0
router1(config-if)# ip address 160.10.1.1 255.255.255.0
router1(config-if)# ip nat inside
router1(config-if)# interface serial0
router1(config-if)# ip address 175.10.1.1 255.255.255.0
router1(config-if)# ip nat outside
router1(config-if)# no shut
