Today we will talk about NAT. Network address translation (NAT) is the process by which one or more local private IP address pairs are translated into one or more global (public) IP addresses. This is done so that the local host is given the facility of internet access. NAT usually works on the router or firewall ie it is configured in it.
How work NAT
Now let's talk about its working, most of the router's border is configured for NAT. This means that such a router, which has one interface in the local ie the inside network and one interface is in the global network ie the outside world.
When a packet is sent from local network ie from inside, then NAT translates that local ie private IP address into global i.e. public IP address and only its translated address is visible to the outside world. .
But when the packet comes in the local network ie the key comes inwards, then the work of converting the global i.e. public IP address to local i.e. private IP address is done.
If the NAT does not have an address to provide, it means that there is no address left in the configured pool, and the packet is then dropped and notified by sending an Internet Control Message Protocol (ICMP) message. that the destination cannot be reached yet.
Configuration of NAT click on followings link
https://www.chachaji.in/2021/01/network-address-translation-nat.html