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Grabmyip->Networking Guides->Nat/Pat

What is NAT/Pat? How do I use it?

Network Address Translation or NAT is an active process on a router, or firewall that typically connects to another network (in most general cases, The Internet). Popular as a way to deal with the IPv4 shortage since it utilizes a single address for the benefit of multiple systems. From Wikipedia
In a typical configuration, a local network uses one of the designated "private" IP address subnets (such as 192.168.x.x or 10.x.x.x), and a router on that network has a private address (such as in that address space. The router is also connected to the Internet with a single "public" address (known as "overloaded" NAT) or multiple "public" addresses assigned by an ISP. As traffic passes from the local network to the Internet, the source address in each packet is translated on the fly from the private addresses to the public address(es). The router tracks basic data about each active connection (particularly the destination address and port). When a reply returns to the router, it uses the connection tracking data it stored during the outbound phase to determine where on the internal network to forward the reply; the TCP or UDP client port numbers are used to demultiplex the packets in the case of overloaded NAT, or IP address and port number when multiple public addresses are available, on packet return. To a system on the Internet, the router itself appears to be the source/destination for this traffic.

See also:
Port Forwarding

Outside links:
Resource of common routers and how to configure NAT/Port forwarding
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