Network address translation: How to avoid common problems

If two or more devices on your home network are performing network address translation (NAT), you might experience the following problems:

  • You can't connect to other PCs over the Internet (for example, you might not be able to transfer files in instant messaging apps or use voice or video chat).

  • You can't connect to other PCs on the same home network (for example, you might not be able to share files).

To avoid these problems, it's a good idea to have only one device in a home network perform NAT. Any other devices should be in bridge mode—a setting that allows data to pass directly through devices without the protection of NAT—and should connect to the device that's performing NAT (or to a device that's connected to the NAT-performing device). Here are two examples of networks that are set up correctly:

  • Network A has a modem with an internal router that performs NAT, a wireless router in bridge mode, and a number of other devices connected to the modem or the wireless router.

  • Network B has a modem with an internal router in bridge mode, a wireless router that performs NAT, and a number of other devices connected to the wireless router (but not to the modem, because the modem is in bridge mode).

Decide which device on your network should perform NAT. For example, if you have a new router that you'd prefer to use while still keeping your existing modem with an internal router, set the internal router in the existing modem to bridge mode, and then use the new router to perform NAT.

Not all routers support bridge mode. Refer to the info that came with your router or contact your router manufacturer if you have questions about your router’s capabilities.

If a router on your network performs NAT in addition to some other function, such as Voice over IP (VoIP), try to connect it as a device and not a router. For example, you could use its wide area network (WAN) port to connect it to your home network and not connect your PCs to its local area network (LAN) ports.

Illustration of the back of a router, showing the WAN and LAN ports
The back of a router, showing the WAN and LAN ports

If you've tried these suggestions and you're still having problems, ask your ISP if they perform NAT on their network. If so, you might not be able to avoid having two devices that perform NAT. If that's the case, ask your ISP about other options.

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