The process of modifying IP address information in IP packet headers while in transit across a traffic routing device is called Network address translation (NAT).CONCEPT:Private Network uses the private IP address and public IP address is used to access the Internet.Network Address Translation(NAT) is a process to translate one or more Private IP address into one or more public IP address so that localhost can access the Internet.The idea of NAT is to allow multiple devices to access the Internet through a single public IP address.Hence, the correct answer is "option 2".Additional InformationOption 1:Port Address Translation(PAT) translates the Private IP address into Public IP address using port numbers.More than one device can use a single IP address to access the Internet using different port numbers.Option 3:Address mapping is used to map the IP address into different forms.Option 4:Port mapping is the process of redirecting the communication request from one IP address and port number combination to another IP address and port number combination.Three types of NAT are:1. Static NAT: In static NAT, a single private IP address is translated into a single public IP address.2. Dynamic NAT: In dynamic NAT, multiple IP addresses are mapped to a pool of public IP addresses.3. Port Address Translation(PAT): PAT is also called NAT overload.