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Again: if you are a newbie read, else pass this post

(most of the) gateways use NAT: Network adress translation to give computers on a LAN access to the internet all with the same IP.

for...

Vorlin is right: specify your question so whe can help you out.

Gateway: you can use some hardware gateway like Vorlin mentioned above or you can use some software gateway to give your LAN access...