Answer Description
Network Address Translation allows a network device (typically a router) to translate IP Addresses. It it most commonly used to hide internal private addresses and instead translates them to a public address. The translation can be one external IP for many internal IPs or a one to one configuration.
Wikipedia
Network address translation (NAT) is a method of remapping one IP address space into another by modifying network address information in the IP header of packets while they are in transit across a traffic routing device The technique was originally used as a shortcut to avoid the need to readdress every host when a network was moved It has become a popular and essential tool in conserving global address space in the face of IPv4 address exhaustion One Internet-routable IP address of a NAT gateway can be used for an entire private network IP masquerading is a technique that hides an entire IP address space, usually consisting of private IP addresses, behind a single IP address in another, usually public address space
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