Are you a gamer and you can’t connect to your online game? Are you finding that your computer won’t allow you to access secure sites? Double NAT could be the cause of your troubles. Read on to find out more about what double NAT means, potential problems that may occur, and how to overcome these issues.
What is NAT?
To understand double NAT, the first step is knowing what NAT means. NAT stands for Network Address Translation. Put simply, it lets all the devices on your home network share the single public WAN IP address your internet provider assigns. Your router translates between that one public address and the private addresses (such as 192.168.1.x) it hands out to your devices, which also keeps those devices from being directly exposed to the internet.
What is double NAT?
Double NAT means your traffic passes through two devices that are each performing NAT, one behind the other. The most common cause is having two routers in series - for example, when your ISP’s gateway (a combined modem and router) is left in router mode and you connect your own router to it. Each device creates its own private network and translates addresses, so your devices end up behind two layers of NAT instead of one.
Problems with double NAT
For the most part, you likely won’t notice any issues when double NAT occurs. There are exceptions, though. Online gaming, some VPNs, port forwarding, and port triggering can all be affected by double NAT - typically anything that relies on incoming connections reaching a specific device. If those activities misbehave while ordinary browsing works fine, double NAT is a likely cause.
Resolving double NAT issues
If double NAT is causing problems, there are a few setting changes that resolve most cases. The cleanest fix is to put one of the two devices into bridge mode so that only one of them performs NAT.
The first is to set up a PPPoE connection between your modem and router. This can typically be done through the WAN settings of your router. Use your user’s manual or visit the router manufacturer’s website for information on how to access and change these settings. It is important to note that some ISPs require a name and password to change this setting. If this is the case, you will need to contact your ISP or visit their website for more information.
If changing the PPPoE setting isn’t an option, don’t worry – other solutions may be available. Some routers allow you to use what is known as a “bridged mode.” This mode essentially disables both NAT and DHCP. This can be changed through router settings, but again, this isn’t necessarily an option that applies to all routers.
You can also set your router to be in the modem’s demilitarized zone. This setting can be changed through the modem’s settings.
Finally, if you have additional modems and routers connected, you can disconnect those. Having extra modems and routers in your network’s connection can result in a double NAT scenario.
Final thoughts
For most home networks, double NAT is uncommon and often harmless. But when it does cause trouble with gaming, VPNs, or port forwarding, the fixes above - especially putting one device in bridge mode - will usually get things working again.
