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Simple NAT explanation

delphized asked
Last Modified: 2011-09-20
I'd like to have from you a simple and short explanation on how NAT works and how to configure a good NAT on my router.
I don't want to search on the web because I would like to have a all in one compendium here.
Thanks and bye
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Luc FrankenEMEA Server Engineer
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I just wanted a resumè not the hsw page ( I knew it but I'm too lazy to read it)

My router is a US Robotic sure connect 9200 used in ethernet mode with a switch and four computer connected (XP and 98)
Top Expert 2009

NAT allows you to use the private IP address ranges (,, on your internal network.  It cuts down on the number of registered/public IP addresses needed.  You could use one public/routable IP address from your ISP on the outside interface of the router and use a private IP address range on the internal interface.  For example:

(Outside Interface - routable IP address x.x.x.x) NAT capable router (Inside Interface - private IP address

Without NAT, a client on the internal network would not be able to access the Internet as private IP address are not routable on the Internet.  When running NAT, the router would translate the private IP address into the routable IP address of the router therefore providing Internet access to the internal computers.

NAT configuration is automatic on any "home" broadband router but configuration is needed on a Cisco router for example.  Let us know which router you are using so we can help with a specific configuration.


but exactly what can you do with NAT ? you can only use it to go outside the router or can it be used to augment the security?
Top Expert 2009
This one is on us!
(Get your first solution completely free - no credit card required)


much better! thanks and have a good day

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