NAT issue

[olly ahmed]

Can anyone clarify the difference between the commands "ip nat inside source and ip nat outside source"  ? Specially I want to know when we should use "ip nat inside source" and when "ip nat outside source".

[Giuseppe Larosa]

Hello Ollyahmed,

the most used command is 

ip nat inside source ...

that means that source IP addresses coming from a NAT inside interface and having to go out a NAT outside interface have to be translated according to the command (using a pool or interface).

The ip nat outside source would be applicable to traffic flows that start from NAT outside and are directed to a NAT inside interface, but in real world these addresses do not need to be translated because they are already public IP addresses.

Edit:

there is some use cases for ip nat outside destination when using NAT to perform translation of destination addresses for flows coming from outside. This can be a virtual IP address representing a pool of addresses.

Hope to help

Giuseppe

[olly ahmed]

Thanks for your reply. Sorry ! the question should be, when we should use "ip nat inside source static" and when we should use "ip nat outside source static" command to configure static NAT configuration. I am actually in a confusion about why we use one of them though as far as I know that both commands help us to access the private addresses from out side our LAN.