NAT(Network address translation) tutorial

 NAT(Network address translation)

What is NAT?

• To access the internet one public IP address is needed in our private IP address in our private network.
• The idea of NAT is to allow multiple devices to access the internet through a single public address.
• Network address translation(NAT) is a process in which one IP address is translated in to one or more global IP address and vice versa in order to provide internet access to the local hosts.
• NAT generally operates on router or firewall.

Working of NAT?

• Generally, the border router is configured for NAT.         i.e.- The router which has one interface in local (inside) network and one interface in the global (outside) network.
• When a packet traverse outside the local (inside) network, then NAT converts that local (private) IP address to a global (public) IP address.
• When a packet enters the local network, the global (public) IP address is converted to a local (private) IP address.

                Types of NAT

1. STATIC NAT:- 

• In this, a single unregistered (private) IP address is mapped with a legally registered (public) IP address.      i.e.- one-to-one mapping between local and global address. This is generally used for web hosting.
• These are not used in organizations as there are many devices who will need internet access, the public IP address is needed.

2. DYNAMIC NAT:- 

• In this type of NAT, an unregistered IP address is translated into a registered (public) IP address from a pool of public IP address.
• If the IP address of pool is not free, then the packet will be dropped as an only a fixed number of private IP address can be treanslated to public addresses, search the destination.

3. PORT ADDRESS TRANSLATION (PAT):-

• This is also known as NAT overload. In this, many local (private) IP addresses can be translated to a single registered IP address, port number are used to distinguish the traffic.

NAT INSIDE AND OUTSIDE ADDRESS

• Inside local address:-  An IP address that is assigned to a host on tinside (local) network. The address is probablly not a IP address signedby the rvice provider.   i.e.- these are private IP address.

• Inside global address:- IP address that represents one or more inside local IP address to the outside world. This is the inside host as seen from the outside network.

• outside local address:- This is the actual IP address of the destination host in the local network after translation.
• Outside global address:- This is the outside host as seen from the outside  network. It is the IP address of the outside destination host before translation.

           ADVANTAGES OF NAT

• The main advantage of NAT is that it can prevent the depletion of IP v4 addresses.
• NAT (network address translation) can provide an additional layer of security by making the original source and destination address hidden.
• NAT (network address translation) provides increased flexibility when connecting to the public internet.

              DISADVANTAGES OF NAT

• NAT (network address translation) is a proccessor and memory resource consuming technology since NAT need to translate IP v4 addresses for all incoming and outgoing IP v4 datagram and to keep the translation details in memory.
• NAT may caause delay in IP v4 communication.
• NAT cause loss of end-device to end-device IP traceability.