NAT

Prerequisite knowledge

• IP Address
• Network Router
• Network Port
• Computer Network

Abstract

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• Stands for Network Address Translation

• On the Internet, each device is expected to have an unique IP Address. However, IPv4 has maximum ~4.3 billion addresses, less than the total world population. This means no everyone on earth can connect their device to the Internet at the same time. We can solve this by using IPv6 or NAT

• NAT solves the problem by allowing multiple devices on a Local Area Network (LAN) to share a single Public IP Address

NAT Mechanism

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• Since IPv4 is limited, we only assign one Public IP Address to the Network Router we control. The other devices we have are connected to the router with Private IP Address assigned to facilitate communication among the devices we have and the router
• The NAT is basically a table of mappings the router maintains. The table maps the private IP address of the the device and its Network Port to the public IP address of the router and the device’s network port
• So the Server will think it is communicating with the router. When router receives a request back from the server, it will check its NAT table and forward the data back to the corresponding device