NAT Protocol Simplified Explanation

  • The purpose of NAT protocol is to reduce usage of public IPs
  • A host needs a public IP to connect to Internet
  • If the host is part of a LAN with a gateway router, a host can use private IP to make requests to public Internet.
  • The public Internet would see that all the requests are originating from a LAN (i.e. the gateway router)
  • A router has a local LAN IP and a public IP.
  • The request flows as following:
    • A local host in the LAN can make a request to a web server on Internet.
    • The host request goes frpm local host IP and port to the local gateway.
    • The gateway maintains a NAT table.
      • An entry in the NAT table will have the source and destination mapping
        Local Host IP | Local Host port | Gateway public IP | Gateway port |
        • The gateway creates a port that maps request to and from the local host to the public Internet web server.
        • Hence the public server would always see the gateway IP and port and LAN host would be anonymous.
      • NAT is essentially a kind of multiplexing local hosts requests over gateways single IP and multiple ports, assigned to each local host.


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Forgot wifi router password? How to update it on Windows?

  • Assuming you are on your wi-fi.
  • Go to run, and type ipconfig. The gateway IP is the IP of your router.
Windows IP Configuration
Wireless LAN adapter Wireless Network Connection:
   Connection-specific DNS Suffix  . :
   IPv4 Address. . . . . . . . . . . : 192.168.x.x
   Subnet Mask . . . . . . . . . . . :
   Default Gateway . . . . . . . . . : 192.168.x.x
  • Open a browser, type the router IP as the target address
  • An authentication pop-up would flash. Enter user ID and password. Cisco router use admin/admin.
    • Search here for default user ID and password. Click here
  • Go to wi-fi tab, set your new password
  • Restart your router.
  • Done 🙂