Читать книгу Networking All-in-One For Dummies - Lowe Doug, Doug Lowe - Страница 60

When a router is used to connect a private network to the Internet, one of the router’s most important functions is routing traffic from all the computers on the private side of the router to the public side, which usually has just a single public IP address. To accomplish this magic, the router uses network address translation (NAT).

In short, when a computer on the private side of the network sends a packet through the router to the Internet, the router substitutes its own public IP address as the sender address, and keeps track of the fact that it sent a packet on behalf of a computer on the private side. When the recipient on the Internet receives the packet, it sees that the sender was the router. It then sends a response back to the router, which then substitutes the original sender’s private IP address for the destination address and forwards the packet to the correct computer on the private network.

For more information about NAT, see Book 2, Chapter 3.