Prerequisite knowledge
Abstract
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Stands for Network Address Translation
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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
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NAT solves the problem by allowing multiple devices on a Local Area Network (LAN) to share a single Public IP Address
Important
Port Address Translation(Outbound) is the most common form of NAT. There are another 3 types of NAT.
DNAT (Dynamic NAT) primarily handles outbound traffic. It dynamically maps internal private IP addresses to the router’s public IP address(es). This allows multiple devices on the private network to share a limited number of public IP addresses when accessing external resources.
Port Forwarding (Inbound): This technique directs incoming traffic from a specific port on the router’s public IP address to a designated port on an internal device with a private IP address. This is often used to make services like web servers or game servers accessible from the internet.
SNAT (Static NAT) primarily handles inbound traffic. The router possesses a pool of public IP addresses, each of which is mapped to a specific internal private IP address. This allows external devices to initiate connections to devices within the private network.
Port Address Translation
- 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 deviceand its Network Port to thepublic IP address of the routerand 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