How NAT Handles Your Internet Requests

May 12, 2020 By Nick Anderson No Comments 5 minutes

There is an estimated 30+ billion devices in the world right now. The devices connect to the internet and communicate to fulfill their functionality. The staggering figure will only grow, and it’s expected that more than 76 billion devices will be online by the end of 2020.

Much of the figure is due to IoT devices that use the internet to communicate with other devices. But while we’d all love to have the internet power everything, there are some limitations. There are just not enough IP addresses to give every would-be connected device access to the internet.

NAT was created because this was an inevitable situation. We’ll explain to you how NAT resolves the issue, and how it’s used to communicate with other devices over the internet.

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How NAT Works

NAT stands for Network Address Translation. The sole purpose of NAT is to make communication over the internet possible by converting private IP addresses to a public IP address.

A private IP address is the one assigned by your router. It lets the router uniquely identify each device connected to the network. NAT comes in play when you request to communicate with devices outside of the network or on the internet.

There are only so many IP addresses available. As a 32-bit protocol, IPv4 allows around 4 billion unique IP addresses. The actual number is a little less because some IP addresses are reserved for special cases. NAT works to lessen the effect of the growing number of devices coming online.

Instead of giving every device in your home a unique IP address, the ISP assigns you only one that serves a block of devices.

Go to whatismyip.com and note the IP address. Now, if you checked your router or LAN/Wireless connection, your IP address would be different. That’s NAT working its magic.

Think of NAT as a servant in a home. Family members order what they want from the market, and the servant heads to the market to fetch the required items. Upon return, the servant checks his list to see who in the family ordered what and distributes it. NAT works in a similar way.

Multiple devices in your home are communicating on the internet through a common router. The requests from each device make a stop at the router, then NAT translates the private IP address and assigns a public IP address. The request travels the internet, reaches its destination, then returns to your ISP and your router. NAT looks up its table to check the corresponding private IP address and efficiently delivers you the result without any errors.

It all happens so quickly and without your knowledge. But NAT is there, working everytime you communicate to a device outside your network.

IPv6 is the next step forward in the evolution of the network infrastructure. As a 128-bit address, it provides an incredible number of IP addresses; try calculating the 2^128, and you’ll understand.

But IPv6’s rollout has been slow. Between retrieving old IPv4 addresses and implementing IPv6, it’s going to be a while before IPv6 is mainstream.

Following are the types of NAT:

Static NAT

The first type of NAT masks a private IP address to a public IP address. So, everytime the IP address accesses the router, it will always be assigned a specified IP address. It’s useful when you are communicating with a device from outside your network.

Dynamic NAT

Dynamic NAT takes a private IP address and assigns any from a range of public IP addresses. NAT will ensure that traffic entering the router will be sent back to the device that originated the request.

Overloading NAT

In this approach, internal IP addresses will be assigned to a single public IP address. PAT (Port Address Translation) is responsible for returning packets to the correct device by looking up ports.

Double NAT – How to Fix NAT Issue

Double NAT is when you have two routers performing NAT. If you have a modem/router from your Internet Service Provider and you have another router connected to it, NAT translation can cause issues in some cases such as playing games online or establishing a VPN connection.

If you have the same setup, you can identify if double NAT is active.

Open Command Prompt
Type tracert 8.8.8.8

Notice the first two IP addresses. These are routes the request is taking. If the second IP address also falls under the private IP ranges (192.168.0.0 to 192.168.255.255), then you have double NAT active.

You can fix double NAT by setting the first router in bridge mode. Secondly, you can enter the second router’s gateway (likely 192.168.1.0) in the first router’s DMZ. Refer to manuals online on how to configure your particular router model.

Conclusion

NAT is here to stay for a long time until IPv6 propagates into the mainstream. If you’re not someone playing games online, running a VPN, or accessing a device remotely, then double NAT will cause no issue.

You can learn more about IP address – IPv4 and IPv6 – in our blog here.