Network Address Translation( NAT)

Network Address Translation (NAT) allows you to convert one IP address in to another address. Address Translation process changes the IP address information in a packet to different address. NAT feature is introduced to solve two major issues faced in networking: face the shortage of IP addresses and hide the network scheme. Now the major function of Address Translation is to convert the private IP addresses in a network in to a public IP address. This tutorial explains the major functions, different types and working of NAT.

Different Types of Address Translation

Address Translation is of different types depends on the way and the number of IP addresses they translate.
  1. Static NAT

    In Static Network Address Translation, one IP address in a packet is translated to different IP address manually. It is one to one mapping.

  2. Dynamic NAT

    In Dynamic Network Address Translation, address translation device picks an IP address dynamically to convert from a list of allowed IP addresses. Dynamic NAT has two set of IP addresses. One is a list of IP addresses which are allowed to be converted and the second is the list of IP addresses which are to be converted. The major problem with static and dynamic NAT is, they convert just one IP address  to another IP address. NAT cannot convert multiple IP addresses to single public IP address or vice versa.

  3. Port Address Translation

    Port Address Translation (PAT) helps all the private IP addresses in the network to use single public IP address with different port numbers. So by using PAT we overcome the limitation of NAT which uses one to one mapping. One disadvantage of PAT is, not all applications work with it. PAT works with only TCP and UDP protocols.

  4. Port Address Redirection

    Port Address Redirection (PAR) is the reverse of PAT. In PAR, multiple public IP addresses will be converted to single private IP address. PAR too works with only TCP and UDP protocols.

Major Benefits of Network Address Translation
  1. Address Translation fixed the scarcity of IP addresses

  2. NAT successfully hides internal network design from external parties

  3. NAT helps network admins to have tighter control over network traffic

Disadvantages of Address Translation

Though NAT is very helpful, it is not free from disadvantages. Some of them are:
  1. PAT and PAR works with only TCP and UDP protocols

  2. Not all applications support Address Translation

  3. Address Translation cause extra delay in each connection

  4. NAT makes network troubleshooting more complex

Recommended Tutorials
  1. Dynamic Host Configuration Protocol (DHCP)

  2. OSI Reference Model

  3. Virtual Router Redundancy Protocol (VRRP)

  4. What is a Router & Major Routing Protocols

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