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NAT double, the cause of a slow Internet or «LAG»

Doble NAT, causa de un Internet lento o con «LAG»

Normally, the internal internet service, which is you, me and most of us at home, usually comes configured with a dual NAT mechanism. The acronym NAT stands for «Network Address Translation» or Network Address Translation. Double NAT obviously means that a double translation of the network address is done at our connection. Of course, this tells us absolutely nothing, so we will leave aside these technical aspects that we can read much better on Wikipedia to focus on the practical nature of the problem. That is, what is basically double NAT, how to know if you have a double NAT in your internet connection and how to remove that double NAT.

What is double NAT

What is Double NAT: Source: Ubisoft

Dual NAT, in practical terms, means that you are not directly connected to the Internet, but there is a second router after the one you have at home and before you reach the Internet («Second router», in the illustration above).

When you open a webpage or generally connect to the Internet, your request goes first through your home router and then through a second router owned by your ISP. That is, it must go through two networks, home and ISP, before reaching the Internet. This is why it is called Double NAT, because packets must be converted or «translated» twice, from one network to another, to reach the destination.

ISPs often set up home internet service under dual NAT to reduce costs. The price of the service would be high if it gave us direct access to the Internet for each customer, so what they do is group several users in an area or sector under a single router and thus all those people connect to the Internet. More technically, they form a private network of customers (each with a private IP) and provide access to the Internet to all through a single router with a public IP that has direct contact with the Internet. If it were not for this double NAT, each client would have to have its own public IP, which would significantly increase the cost of the service.

This obviously has an impact and REMARKABLE, in service speed (in addition to connectivity, as we saw in the opening of ports). Even if well implemented, the NAT double is perceived mainly negatively in the «reaction» or «instantaneity» of the service, ie the pages or videos need time to open or there is a latency or gap in online games.

How do I know if I have double NAT

Public IP fast on the internet

To find out if you have dual NAT, you need to enter the router configuration and check the IP address in the WAN Information section. If it’s different from the IP address you get in the «What’s my IP» online pages, then you probably have double NAT.

The procedure is generally similar for most routers or modem (s). For the sample, I will explain how I did it on my Huawei HG8546M modem / router:

  1. Enter the router configuration. From a web browser connected to the router, go to its configuration page. In my case, the default access address is In the router page you have to enter the username and password, which in my case is root and admin. You should consult this data for your particular router model on the Internet or with your provider (if the latter has changed the default data).
  2. Once in the router configuration, you should look for an option similar to «WAN Information» or «WAN Information», which in my case is in the menu on the left, as seen in the illustration above.
  3. On the right you will find the information we are interested in, ie the IP address of your connection (in the «IP Address» field). In my case, I must first click on the connection name («1_INTERNET_R_VID_51») to expand this information. Write down this IP address for the comparison below.
  4. Finally, you need to go to any of these online pages and compare the IP address they show you with the one you noted in the previous step. If the IP Not it’s the same, so you have a dual NAT connection. If it is the same, then fortunately you have a simple NAT or an internet service with a public IP.

How to remove double NAT

The only way to remove dual NAT and «bypass» that second-mentioned router between us and the Internet is to request a public IP from your provider. This change converts dual NAT to single or single NAT. In other words, the second router I mentioned «disappears», so that your router connects directly to the Internet and there are no barriers between them, so that the «response» of the Internet service improves and becomes more immediate.

The disadvantage of public IP is that it is usually a subscription and not a one-time payment. That is, it will have an additional monthly cost for the one you already pay for your internet service. For example, in Ecuador, some Internet service providers charge $ 5 and others charge $ 10. This is a good thing, because in some cases you will not even have this possibility. Some ISPs will only assign you a public IP if you purchase a corporate or business plan, which usually costs twice or three times as much as an internal plan.


Slow internet service can have several causes. It is likely that your computer, mobile phone, router / modem and its weak signal or even wiring. Your ISP is probably the last thing you should look at. And if that’s the case, maybe your ISP is offering you a dual NAT service. In itself, this is already an issue that affects the speed of the service and, if poorly implemented, the problem of slowdown will be even greater. Purchasing a public IP to bypass dual NAT is definitely a way to improve your internet service. In terms of experience, it will probably give you as much as buying a higher or «mega» speed plan. This is especially true if you want an immediate response from your internet, which is especially needed in online games.

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