Network Address Translation

The Internet and IP-related technologies have experienced rapid growth. One reason for the growth has been due in part to the flexibility of the original design. However, that design did notanticipate the Internet's popularity and the resulting demand for IP addresses.
To cope with the depletion of IP addresses, several short-term solutions were developed. Two short-term solutions are privateaddresses and Network Address Translation (NAT).
NAT enables inside network hosts to borrow a legitimate Internet IP address while accessing Internet resources. When the requested traffic returns, thelegitimate IP address is repurposed and available for the next Internet request by an inside host. Using NAT, network administrators only need one or a few IP addresses for the router to provide tothe hosts, instead of one unique IP address for every client joining the network.
NAT-enabled routers retain one or many valid Internet IP addresses outside of the network. When the client sendspackets out of the network, NAT translates the internal IP address of the client to an external address. To outside users, all traffic coming to and going from the network has the same IP address or isfrom the same pool of addresses.
NAT has many uses, but its key use is to save IP addresses by allowing networks to use private IP addresses. NAT translates private, internal addresses into public,external addresses. NAT has an added benefit of adding a degree of privacy and security to a network because it hides internal IP addresses from outside networks.

There are two types of NATtranslation: dynamic and static.

Dynamic NAT uses a pool of public addresses and assigns them on a first-come, first-served basis. When a host with a private IP address requests access to the Internet,dynamic NAT chooses an IP address from the pool that is not already in use by another host. This is the mapping described so far.
Static NAT uses a one-to-one mapping of local and global addresses, and...