What is a Network Address Translation (NAT)

Network Address Translation the method used to remapping the IP address space of packet to another by changing the network address transformation when they are transmitting through a router. When the network has moved this method is mostly used to avoid the readdressing of the host. These become the essential tool in global address space in ipv4 address. The technique used to hide the address space is IP masquerading which contains the private address behind public address space. to know more about What is a Network Address Translation (NAT) keep reading this article till the end.


This is the simplest way of NAT as basic NAT which provides one –to- one translation of IP address.it is also known as one to one NAT. In this type of NAT, the IP address got changed if the IP address contains IP address, IP header checksum, and higher-level checksum. This type of NAT can be used to connect two networks which have a different address.


LAN uses one of the built-in private addresses of the subnets. The router in that network contains a private address in the address space. This router is connected with the network using the public address which is provided by the ISP. When the packets are transferred from local networks to the internet, each packet is translated to a form where they can move from private addresses to the public address. The router tracks each data for its active connection. When a reply return to the router, it uses the data connection to determine the private address of the packet. Every IP packets have their source address and destination address. Firstly when the source address is get modified when they are changed from private to public address, after the destination address get changed when public network change to the private network.


There are different ways of implementing network address and port translation. IP address information is used by some application protocols to determine the external NAT address. These are used to detect the communication peers, and also to know the type of mapping used. Mainly these are set to know the direct communication path between two clients separated by NAT. STUN (Simple Traversal Of UDP over NAT) protocol is used for this purpose and id developed in 2003 March. This protocol classified NAT into

  • Full-cone NAT
  • Restricted-cone NAT
  • Port- restricted cone NAT
  • Symmetric -cone NAT

Full-cone NAT

           It is also called as one-to-one NAT. when internal address gets aligned with external address any packet from internal can send to the external address. Likewise, internal packets can receive packets from external host also.

Restricted-cone NAT

           Here packets can be sent through the internal address from external address when internal and external addresses get aligned. If the internal address has sent the packets to the external host previous time, then only the external host can send the packets to the internal address.

Port- restricted cone NAT

Here port numbers are restricted. Once internal and external addresses get aligned they can send packets to each other. Like restricted cone, if the internal address has sent packets previously to external host then the only external host can send packets to the internal address.

Symmetric -cone NAT

           Requests from the same internal address and port to a specific destination are aligned to a unique source IP address and port. The external host can receive packets from the internal host and can send packets back.

TYPES OF NAT, Different types of NAT are:-

  • DNAT
  • SNAT

DNAT (Destination Network Address Translation)

  The technique is used to change the destination address of the end routers. The router placed at the end of the routers can perform this technique.

SNAT (Secure Network Address Translation)

 The technique is used for tracking and filtering the network connection used for FTP, PPTP, etc. and to analyze the arrangement of the proxy server.

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