Network Address Translation (NAT)

Why do we need this?

Not practical for homeowners to have to understand ip address, and configure it for each device.

Not scalable as well, one can have many devices.

How to abstract this concern away for homeowners?

  • Permit hosts to change ISPs without changing addresses of hosts in the local network.

  • To do so we can have private IP address ranges that will not be used on the public Internet. Address spaces within these private ranges can thus been used for hosts on private networks.

  • Network Address Translation: Translates data- grams containing these private addresses to use the router’s IP instead.

How do external parties communicate with homeowner?

  • To the public Internet, it looks like the all the devices are actually one device, which is the NAT-enabled router itself.

  • NAT Translation Table: For each host in the private network, a specific port on the router will be used for it. It stores the IP address and port number for the WAN and LAN sides.

How does it protect local devices?

  • Hosts inside a network are not explicitly addressable.