What Is Double NAT? | Quick Guide

A reliable internet connection is important for everyone on the internet, whether you need it for gaming or work purposes. However, there are occasions where you encounter problems with your connection. Sometimes you may be unable to host a game, and other times, all your efforts to join a server fail.

There are so many things that cause those connection problems, such as Double NAT. This is one issue you may not even know you’re experiencing, even though it could cause serious problems for some of your applications and hardware.

A lot of people are not familiar with Double NAT and have possibly never heard of it. Well, this article will discuss Double NAT in detail to help you understand what it means and its implications on your connectivity.

What Is NAT?

Network Address Translation (NAT) is the process where all your devices share a single address provided by your Internet Service Producer (ISP). This happens when your public IP address is changed to a private IP address inaccessible unless you go through the protocol. NAT is also vital for firewall security.

NAT secures your home or work network by blocking direct access to your local IP address and hiding your network away from unauthorized parties. It also translates port numbers, i.e., cloaks the host’s port number with another one in the data packet that will be routed to an address. NAT then enters the corresponding IP address and port number in the NAT table. Routers or firewalls are responsible for the NAT.

There are three types of NAT:

Static NAT

You have a static NAT when just one private IP address is mapped with a public IP address. This is typically used for hosting websites.

Dynamic NAT

This type of NAT translates a private IP address to a public IP address from a pool of public IP addresses.

Port Address Translation (PAT)

In Port Address Translation (PAT), many private IP addresses are translated to one public IP address. Port numbers are used to tell which traffic is from a particular IP address. PAT is also called NAT overload. It is frequently used because it is cost-effective as multiple users can connect to the internet through one public IP address.

Advantages of NAT

Some of the benefits of NAT are:

1. NAT provides privacy by hiding the IP address of devices and data traffic.

2. In addition, it gets rid of address renumbering as a network evolves.

Disadvantages of NAT

Although NAT is helpful, it has several disadvantages such as:

1. Specific applications and services malfunction or stop working while NAT is enabled.

2. It complicates tunneling protocols such as IPSec.

3. Routers shouldn’t manipulate port numbers, but because of NAT, it does.

What Is Double NAT?

Double NAT occurs when you are connected to two routers, creating two private networks. This is usually found in schools, hospitals, and other places with advanced networking. Double NAT still allows you to connect to the internet, but it makes port forwarding almost impossible and causes issues with online games or connecting to a VPN.

Double NAT prevents the users on one private network from communicating with the devices connected to the second private network. It could make it difficult for you to join a chat room or host a game.

With Double NAT, you will have to go through the same setups and configuration on both routers. As a result, it may cause issues when using applications or services that use Universal Play-and-Play (UPnP). It could also be problematic when you try to use the Quality-of-Service (QoS) feature. QoS lets you prioritize traffic on your preferred activities such as torrenting, streaming, gaming, or downloading files.

How To Check a Double NAT

You may not notice Double NAT as it happens. You may not know if you’re on single NAT or Double NAT till you can’t host servers or you start receiving Double NAT errors on your gaming console.

However, there’s a way to check for Double NAT. You can check by pinging any public server through your operating system’s command prompt. You just have to follow these steps:

  1. First, open a command prompt on your OS.
  2. Type the following: tracert 8.8.8.8. It is Google DNS.
  3. Check the first two hops for the IP addresses.

If the first two hops display private and public addresses, it means you’re on single NAT. But if the first two hops are personal IP addresses, you’re using a Double NAT.

How To Fix a Double NAT

If you have checked and seen that there is a Double NAT problem, here are a couple of tips to help you fix it:

1. Remove the ISP Router from Your Network

The simplest way to fix Double NAT is to remove your ISP router and connect your internet and other devices to your preferred router. This gives you a single NAT, free of the problems with online gaming, port forwarding. 

2.  Enable Bridge Mode on Your ISP Router

If you’d prefer to keep your ISP router, you can use the Bridge Mode function to make your router a passthrough modem.  You can enable it through these short steps:

  • First, go to your router’s login page.
  • Then, enter your credentials to continue.
  • Next, you will need to find the wireless settings on your router.
  • Enable Bridge Mode.
  • Once you’re done, save the settings.

How To Fix Double NAT on Your Router

If your router doesn’t support Bridge Mode, it’s not the end of the world. You can still get rid of the Double NAT issue if you make your non-ISP router an Access Point. Making it an Access Point works like the Bridge Mode, and removes the router’s NAT functionality. Here is how to enable Access Point (AP) mode:

  • First, you’ll have to visit your router’s login page.
  • Next, enter your login credentials.
  • Proceed to the wireless settings on your router.
  • Enable the Access Point (AP) Mode.
  • Finally, save your settings.

How To Fix “Double NAT Detected” Error on Xbox One

If your Xbox is displaying a “Double NAT Detected” error in the network setting, it means that your console is connected to multiple routers. If that’s the case, you can fix the issue through any of the methods we discussed above. However, if the method’s don’t fix the error, you can fix the error with any of the following ways:

1. Use Perimeter Network (DMZ) to Forward Connections

Here’s how to do it:

  • Log into your non-ISP router.
  • Find the WAN/IP Address on the status page.
  • Log into your ISP router through WiFi or ethernet connection to a WAN port from a PC.
  • Head to the DMZ setting page.
  • Use the IP address from step 2 to enable DMZ.
  • Once you’re done, save the settings.

2. Use Double Router Port Forwarding

Alternatively, you can follow these steps for port forwarding:

  • Log into your first router.
  • Forward ports to the other router’s public IP address.
  • Next, log in to your other router.
  • Forward port to your gaming server or other applications you want to use.
  • Configure the static IP address on the other devices and confirm that the second router is configured for static IP.

How To Set Up a Static IP address on Windows 10

Here are the steps for setting up a static IP address on Windows 10:

1. Open Command Prompt.

2. Type ipconfig/all.

3. Locate your Network Adapter, and note the IPv4 Address, Subnet Mask, and DNS Servers.

4. Go to your router’s Status page to confirm if the DNS servers have the same IP as the Default Gateway.

5. Open the Settings on your Windows 10.

6. Click on Network & Internet and proceed to Change adapter options.

7. Right-click to open Properties.

8. Select Internet Protocol Version 4 (TCP/IPv4).

9. Go to Properties.

10. Write down the current configuration.

11. Next, select ‘Use the following IP address’ and choose an IP address for your PC.

12. Enter the Subnet Mask and Default Gateway.

13. Go ahead and click ‘Use the following DNS server addresses.’

14. Enter the two DNS servers that you noted from your router‘s status page.

15. Finally, click ‘OK’ when you have finished the configuration.

Conclusion

Double NAT is not essential to everyone online. As we said earlier, you may not know you’re on a Double NAT network unless you start to have problems or notice Double NAT error messages as you try to access online games and other services.

However, there are straightforward steps to check if you’re on Double NAT, and we have highlighted them in this article. Furthermore, if you are having issues because of Double NAT, you can follow our guide to fix it quickly.