What is Double NAT and How Can You Fix It?

December 23, 2021 By Nick Anderson No Comments 5 minutes

NAT is an integral part of routers, ensuring the reliable transmission of data packets to the source that requested it. It is part of every network device that features routing functionality. Where NAT solves many problems, it can create new ones like Double NAT. Wondering what Double NAT is and how you can fix it? This is the blog for you.

What is Double NAT

How Does NAT Work?

Network Address Translation (NAT) is built into every router for the purpose of delivering network traffic to the right recipient. When you request to open a website on the internet or communicate with any device on the local network, NAT keeps a record of everything.

NAT is like a register that keeps a list of every incoming and outgoing request. All devices connected to the router have an IP address and MAC address that distinguishes them on the internet. NAT is important because the router will not know where to send back the requested data without it.

It was created to slow the exhaustion of IP addresses. As there are a finite number of public IP addresses that can be generated from IPv4 and IPv6, networks were split into private and public networks. It allowed private networks to exist separately and not affect the distribution of public IP addresses. The situation will improve once IPv6 becomes mainstream.

In short, NAT allows private networks to access the internet via a single public IP address.

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What Causes Double NAT?

Double NAT occurs when you connect two routers and both are handling NAT. Having NAT enabled in both routers will create two private networks.

Depending on what device your Internet Service Provider (ISP) provides, you might either have a modem or a modem and router combo. The easiest way to spot a router is to check if it supports more than one LAN connection or has Wi-FI capability.

Once you connect devices to a second router with NAT enabled, it will be another private network inside the network that’s run by the first router. Double NAT raises several challenges for inbound traffic and when you try to communicate with devices inside the second network.

How Does Double NAT Affect You?

In the age of the Internet of Things (IoT), there are more smart devices and appliances in homes than ever before. These smart devices connect to a common network so that they can talk to each other and make your life easier.

It is possible to access smart devices remotely through the internet. For example, you can remotely access the security cameras in your home while you are at work. The private network of your home can be accessed through the internet as long as you know the IP address of your security camera. But if the security camera or any other IoT device is behind another private network,

Another area where double NAT is problematic is games. Components of online gaming such as voice communication are severely affected if NAT is not properly allowing the ports to open.

Manual port forwarding is a process of allowing specific ports so that incoming traffic can get past the firewall easily, but this can’t extend to the second router because it is a different network. Similarly, if you have ports open on the second router, it will not matter because the first router will restrict the ports and will not know where to send that incoming traffic.

How to Turn Off Double NAT

You can turn off double NAT by disabling NAT on the second router so that it works as an extension of the first router.

Open your router’s admin panel.
Disable the DHCP server in the DHCP menu.
Set your LAN IP address the same as the primary router’s subnet. For example, if your primary router has a network of 192.168.0.xx then choose an IP address 192.168.0.10 (or anything other) for the second router. The IP must be in 192.168.0.xx subnet and its defined range (192.168.0.1 to 192.168.0.199, for e.g).

You can also set the router in Bridge Mode via Wi-Fi. You can learn more about Bridge Mode in our blog here.

Routers have the functionality to be set up in bridge mode if you already have a primary router. This will allow you to control certain aspects of the router, such as bandwidth control, IP assignment, and other DHCP aspects directly from the primary router.

Find the bridge mode option in the router’s settings and enable it. Then, connect the second router to the primary router’s Wi-Fi. Once they are both connected, the second router will act as an extension and automatically get all DHCP configurations from the router.

Conclusion

With all that said, you shouldn’t play around with the settings if the disadvantages of double NAT do not apply to you. It will not be an issue for most people. Double NAT does not affect your everyday streaming and browsing on the web.