What is NAT loopback?

Suppose you have configured an IP camera that you want to access from anywhere via the Internet and have an external IP address, or a DDNS address, to access the camera. Have you tested your configuration when I was away from home, the external network, and everything worked fine,as expected. But you come home and try to use those same addresses to access the camera and nothing appears, or worst, You receive an error message.

You may be witnessing what is called NAT loopback. This peculiarity of router configuration often causes problems for new users and can be very frustrating. This post tries to explain why this happens and what you can do to get around it.

Why does it happen?

To understand what is NAT loopback, you need to understand how your router works. See a simple demostrada network below.

Your camera and computer are, very likely, connected to a router (connected directly by cable, or through a wireless connection), what is, from the router, connected to the Internet through your ISP (ISP – Internet Service Provider). The router has two IP addresses: an internal which is only accessible from your home network (for example 192.168.0.1) and which is accessible from the Internet. To remotely access, you type the external IP router, since using the Internal IP will not work on the external network.

Your local network only understands the type 192.168.x.x addresses. For example, if you typed 192.168.0.2 no browser, your network must understand that you are trying to access the camera and send the information there. Whenever a different address is required (as an external IP address, as 88.20.20.20 or a Web address as minhacam.dydns.org) your router realize that this address is not giving your internal network and sends the information to the Internet.

However, if that external address (as minhacam.dyndns.org), actually, points back to your home router, it will be recognized and the information sent is passed back to your router. Now, or router, then, directs this information back to the correct location on the internal network (as your IP camera) or eliminates data entry packets.

One of the biggest problems NAT loopback It is that it is often not obvious that everything is configured correctly. Some routers will display their own configuration page, when such a request is made by the internal network. Some simply will not show anything, while others are smart enough to recognize what you are trying to do and will refer you to the right place.

This cycle is called auto-retorno NAT (NAT loopback) and some routers allow this function, while others do not. If your router supports NAT loopback you will not see this as a problem, since your camera will be accessible from all locations with the same address, but since you are reading this post, looking for a solution because your IP camera is not accessible, your router probably does not support this function.

How can I fix this?

There are just a fix for this. This is at the discretion of your router. If your router supports NAT loopback, so great! Whenever you enter the external address, will access the camera normally. If your router does not support to this, there is not much you can do.

If your router does not allow NAT loopback, your only option is to use your external address (minhacam.dyndns.org) to access the IP camera when you are not at home, and use the local address (192.168.x.x), When you are at home. Set the addresses favorites and this is not really a problem, although frustrating.

The only other thing to do is get a router that allows NAT loopback, though, often, router specifications do not say if there is support or not, so if you want a router with support NAT loopback, You will have to ask the manufacturer.

There is another potential solution, which aims to change your local address file to point the external address to the camera's internal address. However, this is complicated, so let's deal with this in another post, later.

Source: Network Webcams