IP NAT inside source/ IP NAT outside source

如何能更好的理解IP NAT inside 和outside？

ip nat inside source 
Translates the source of IP packets that are traveling inside to outside.
Translates the destination of the IP packets that are traveling outside to inside.


ip nat outside source 
Translates the source of the IP packets that are traveling outside to inside.
Translates the destination of the IP packets that are traveling inside to outside.


ip nat inside destination 
Translates the destination of IP packets that are traveling inside to outside.
Translates the source of the IP packets that are traveling outside to inside.


ip nat outside destination 
Translates the destination of the IP packets that are traveling outside to inside.
Translates the source of the IP packets that are traveling inside to outside. 

1.inside source ：这种NAT 是数据初始于inside一方向outside 方发送，在outside接口执行翻译，把源地址翻译的动作。
2.outside source：这种NAT是 初始于outside一方 向inside方发送，在inside接口执行翻译，把源地址翻译的动作。

3.inside destination: 这种NAT 是连接初始于outside 一方，向inside方发送，在outside接口执行翻译操作，把目标地址翻译的动作。
4.outside destination：这种NAT是初始于 inside方向，向outside方发送，在inside接口执行翻译，把目标地址翻译的动作。
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note：

inside souce 记成，把inside作为源，这样就是inside向outside方向， inside destination ：把inside作为目的，那就是outside向inside 发送
outside source就相当于把outside 作为源，所以就是outside向inside方向初始， outside destination ：相当于把outside当目的，所以就是inside向outside初始