Network Address Translation(NAT)

NAT is the process of mapping an internet protocol(ip) address to another so that a router can access resources outside a private network.

How Does NAT Work ?

NAT occurs between an internal IP and an external IP via a router.
A computer inside a network makes a request to a computer on the internet. Routers within that network recognise that the request is not for a resource inside the network so the routers act as agents between the public network and the private network, then sends the request to the firewall. The firewall sees the request from the computer within the internal IP, then makes same request to the internet using its own public IP address. The firewall then returns the response from the internet resource to the computer inside the private network.

Ways By Which NAT Can Map IP Addresses

1. From a local IP address to one global IP address.
2. Hiding an entire IP address space comprised of Private IP addresses behind a single IP address.
3. To a large private network using a single public IP address.
4. From a local IP address to a pool of public IP addresses.
5. From a global IP address to a pool of local IP addresses.

Types Of NAT

1. Static NAT: This maps a single unregistered IP Address with
   
   a registered IP address.

2. Dynamic NAT: This translates an unregistered IP Address
   into a registered IP address from a pool of public IP
   addresses.

3. Reverse NAT: This allows users to connect to themselves
   using the internet or public network.

4. Port Address Translation: It is also known as NAT Overload
   or Port-level multiplexed NAT or Single Address NAT. In
   this, many local(private) IP addresses can be translated to
   a single registered IP address.

5. Overlapping NAT: This happens when two organisations whose
   networks uses the same IP address merge or when a
   registered IP address is assigned to multiple devices.

References

1. What is Network Address Translation?.CGP Holdings, Inc.14 May, 2022. https://whatismyipaddress.com/nat.

2. Katie Terrell Hanna. _Network Address Translation (NAT) _.[online]. TechTarget. 14 May, 2022. https://www.techtarget.com/searchnetworking/definition/Network-Address-Translation-NAT.

3.Network Address Translation. Avi Networks. 2022. 14 May, 2022. https://avinetworks.com/glossary/network-address-translation/#:~:text=Network%20Address%20Translation%20(NAT)%20is,private%20network%20a%20public%20address.

4.saurabhsharma56. Network Address Translation (NAT). GeeksforGeeks. 13 Dec, 2021. 14 May, 2022. https://www.geeksforgeeks.org/network-address-translation-nat/