The time comes to hire an Internet line at home and in almost all cases the first thing that catches your attention (beyond the price) is the speed it can offer or if, for example, it is a symmetrical connection. But there is one aspect that can be overlooked and it is important.
When contracting fiber with a telephone operator, it is important to look at a specification that is called CG-NAT (Carrier-Grade Network Address Translation” or “Carrier-Grade NAT”). A technology that directly influences our connection. We will see how it does it and which operators use it.
What is CG-NAT
The acronym “CG-NAT” stands for “Carrier-Grade Network Address Translation” or “Carrier-Grade NAT.” It is a technology used in telecommunications networks and Internet service providers (ISP) to manage the shortage of available IPv4 IP addresses and facilitate the transition to IPv6. This is something that today no longer makes sense or not so much, with IPv6 in our lives. And here may be the key to its use.
CG-NAT works similarly to traditional NAT (Network Address Translation), which is used in most home and business networks to allow multiple devices to share a single public IP address. However, CG-NAT is a large-scale implementation designed to handle thousands or even millions of simultaneous connections.
The main function of CG-NAT is to assign private IP addresses to end-user devices on a private network and then translate those private addresses to a single public IP address before the data goes out to the Internet. This allows multiple users to share a single public IP address, which save public IPv4 addresses and delays the need for full adoption of IPv6.
How it influences our connection
The use of CG-NAT can have implications for some applications and services, especially those that require the ability to receive incoming connections from the Internet, as address translation can make it difficult to establish those connections. This may affect the functionality of some peer-to-peer applications, to play online and to use other services that require specific ports to be open and accessible from outside the network.
Contracting Internet with an operator that uses CG-NAT prevents us, for example, from being able to open ports on the router, since we share a Public IP. The same thing happens if we want to have an FTP server, use a NAS and we will not be able to put any service on our local network.
We will also not be able to do port forwarding because the WAN IP is not public. Our router loses potential and almost becomes a virtual router, since it is the operator that controls a good part of its functions. In the case of wanting to play online, the problems are caused because there is a increased latency during games.
And when it comes to influencing the connected home and the devices that make it up, if they require a public IP there is another problem. These are some examples of the “drawbacks” it can offer.
Likewise, we may be affected in the case of bans. If a user with whom we share the Public IP has been banned from a service, it will be as if you had also been blocked and will not be able to access that website or service.
How to know if I have CG-NAT
When the time comes, How can you tell if your connection uses the CG-NAT protocol? You can check it by following these steps:
- Check the public IP address: The easiest way to check this is to check the public IP address assigned to you by your Internet Service Provider (ISP). You can do this by going to a search engine and searching for “What is my IP?” Your current public IP address will appear.
- Compare the IP address: Once you get your public IP address, compare it to the IP address your ISP provides on your Internet service contract or bill. If both IP addresses match, you are probably not using CG-NAT. This means that you have a dedicated public IP address.
- Contact your ISP: If the IP address you obtained does not match the one on your contract or invoice, you may be using CG-NAT. In this case, we recommend that you contact your Internet Service Provider and ask them directly if they are implementing CG-NAT on your connection.
- Port test: If you have doubts and need more definitive confirmation, you can try opening a port on your router and then access a service or application that uses that port from the Internet. If you can’t connect properly from outside your network, you are probably behind a CG-NAT. This is because CG-NAT can hinder the ability to receive incoming connections.
Which operators use CG-NAT
In this sense, it is necessary to distinguish the operators that adopt CG-NAT in their connections. For example, the Másmóvil Group with Másmóvil, Yoigo and Pepephone They use this system, although they allow you to exit it by contacting customer service.
Digi is another of the operators that use CG-NAT. This means that you share Public IP, but you can have a personal connection by paying a set price per month and contract the Connection Plus Service for one euro per month by calling the customer service number 1200 from a Digi phone.
Another operator that uses CG-NAT is Finetwork in its own fiber . The difference is that in this case it is mandatory and there is no possibility of removing it from the connection. Only in the event that the connection is carried out with the Vodafone fiber network, the user will stop using CG-NAT.
The last operator to bet on CG-NAT is Virgin Telco. This protocol is activated by default and to deactivate it you must contact customer service on one of the social networks in which they operate or by calling 910 053 487.
They do not use CG-NAT operators like Movistar, Vodafone and O2. In the case of Orange and Jazztel, these two operators do not use CG-NAT in their connections, but they do use it in the case of clients that have IPv6 so that they can access services that require IPv4. It is therefore a kind of key to be able to move from one protocol to the other.
In summary, CG-NAT is an IP address translation technology used by Internet service providers to share public IP addresses among multiple end users and extend the life of IPv4 addresses in a world where IPv4 addresses are becoming increasingly scarce.
Cover image | Brett Sayles
In Xataka SmartHome | What is plastic fiber optics and why is it an alternative to PLCs or WiFi repeaters?