How to configure Static NAT on Cisco IOS Router

Hello Mohammad!

The IP NAT INSIDE command indicates that the interface in question is on the inside network. The IP NAT OUTSIDE command indicates that the interface in question is on the ouside network. (I’m sure you got that down, I just want to start from the beginning.) Let’s say the IP address of the inside interface is 10.10.10.1/24 and that of the outside interface is 20.20.20.1/24.

Any traffic that enters the router on the inside interface and exits the router on the outside interface will have the following addresses changed:

Source address will change from 10.10.10.X to 20.20.20.1, destination address will be unchanged where 10.10.10.X is the host on the inside network communicating with the outside world.

Any traffic that enters the router on the outside interface and exits on the inside interface will have the following address changed:

Source address will remain unchanged. Destination address will change from 20.20.20.1 to 10.10.10.X.

So, the purpose of the outside command on an interface is to indicate that this interface is participating in NAT and will have to make the appropriate changes to the source addresses when packets are traversing it.

I hope this has been helpful!

Laz

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