CGNAT for ADSL and Fiber Optics: What it is, how it affects you, and how to manage it with your operator.

Have you ever wondered what CGNAT is and why your internet connection might be affected by this technology? With the expansion of fiber optics and ADSL to thousands of homes, the term CGNAT (Carrier-Grade Network Address Translation) has gained prominence due to its implications for browsing, online gaming, or setting up servers at home. In this article, we offer a comprehensive and up-to-date guide About CGNAT: what it is exactly, how it works, its advantages and disadvantages, how to know if your operator uses it, which companies apply this technology in Spain, and, above all, how to manage it and request a public IP address if you need one.

Discover everything you need to know about CGNAT and make the best decisions for your home or business connection, whether with ADSL or fiber optics.

What is CGNAT and why does it exist?

CGNATacronym for Carrier-Grade Network Address Translation, is a technology that allows Internet service providers to share a single public IP address among multiple users. This is achieved through address translation processes from the customers' internal network to external networks.

The main reason for its existence is the shortage of available IPv4 addresses.The IPv4 protocol, used for decades, offers a space of just over 4.000 billion IP addresses, which has fallen short in the face of the enormous growth of connected devices. Although IPv6 It is designed to solve this problem and is already being progressively implemented, the transition has been slow and costly for operators and users.

Thus, CGNAT acts as a temporary and pragmatic solution so that providers can continue offering Internet connections without exhausting their inventory of public IP addresses. Through CGNAT, dozens or even hundreds of users can share the same public IP.This technique is similar in concept to the NAT your home router already uses, but on a much larger scale and directly controlled by the operator.

The technical operation of CGNAT implies that:

Users' private addresses (for example, 192.168.xx) are translated in the operator's central office to a public IP address.
Each request to the Internet goes through an intermediate node that manages the relationship between the private addresses and the shared public IP.
It's not your router that handles the conversion, but the operator's equipment., so you have no direct control over port mapping or the public IP assigned to you.

Why isn't IPv4 enough and why don't we migrate to IPv6 now?

The shortage of IPv4 addresses is one of the biggest challenges facing the Internet in the last two decades.When IPv4 was designed, it was never imagined that there would be so many connected devices: computers, mobile phones, televisions, cameras, household appliances, cars, etc.

IPv6 solves the problem with a virtually infinite address space, but its adoption has been slow due to compatibility, cost, and the need to update much of the hardware and software of operators, businesses, and users. Many older services, websites, and devices still rely on IPv4, so the full transition will take several years, especially in Spain.

In the meantime, to continue connecting new users and devices, operators are turning to solutions like CGNAT. To understand how it affects your network, you can check out our guide on How do I know if my mobile is free?.

How does CGNAT affect your ADSL or fiber optic connection?

For the average user, browsing the Internet, using social media, watching videos, or streaming with CGNAT is no noticeable difference compared to a traditional connection. However, they do exist significant limitations in advanced or specific use cases:

You can't open ports on your routerThis means you won't be able to host externally accessible services, such as FTP servers, NAS, remotely accessible IP cameras without cloud services, home web servers, etc.
Problems with online games and P2P applications, where port forwarding is key to improving latency and connection quality. Under CGNAT, "strict NAT" is common on consoles, which complicates matches and matches.
Slightly higher latency: While this isn't relevant for streaming or browsing, online gamers may notice a slightly higher ping and, in some cases, fluctuations.
Limitations for remote access and advanced home automationIf you want to access IoT devices, home automation devices, or cameras that don't use cloud solutions from outside your home, you'll have problems.
Shared bans: If another user who shares your public IP is banned from a website or service, you may also be affected even if you have no relationship with them.

In most cases, to browse, check email, or watch content on Netflix, YouTube, Spotify, or any similar service, CGNAT will not have any negative impact and can even provide a little more security, as we will see later.

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Types of NAT and how CGNAT fits into this context

The NAT family of technologies includes several variants:

SNAT (Source NAT): Translates the source address of packets leaving the internal network.
DNAT (Destination NAT): Translates the destination address to redirect incoming traffic to machines on the private network.
PAT (Port Address Translation): Port translation, which allows multiple internal devices to share a single public IP, differentiating connections by port number.

CGNAT is a massive extension of these techniques, applied directly by the operator in its network, multiplying the efficiency of the use of public addresses and adding an additional layer between you and the Internet.

Advantages and disadvantages of CGNAT: two sides of the coin

CGNAT is not exclusively negative or positive, but a tool with pros and cons depending on your needs and how you use the Internet:

Advantages of CGNAT

Allows more users to access the Internet without exhausting the available IPv4 addresses.
Provides an additional layer of security: By not having open ports to the outside and sharing the public IP, it is much more difficult for an external attacker to locate and initiate direct connections with your devices.
Simplifies management for the operator, which can organize and monitor the network more efficiently.

Disadvantages of CGNAT

Unable to open ports, which limits the hosting of services on your local network and restricts certain advanced features.
Difficulties with online games, P2P applications, and device pairing that require incoming connections.
Risk of being restricted or banned due to the actions of othersIf a user with the same public IP address as you is blocked, you may also be temporarily banned from websites, forums, or online services.
Complexities for the Police and Authorities when tracking digital crimes, since a single public IP can correspond to dozens of different people.
Limitations for remote access to your home network or advanced home automation systems, personal servers, IP cameras (if they are not cloud), etc.

How do you know if your connection uses CGNAT?

There are Several easy ways to find out if you are under CGNAT:

Check your public IP addressYou can do this by searching “What is my IP?” on Google or using websites like what-is-my-ip.netIf the address you see does NOT match your router's WAN IP (accessible from your router's advanced management), you are likely under CGNAT.
Check your WAN IP range on the router. If your IP is within the range 100.64.0.0/10, that is, it starts with 100.64.xx, 100.65.xx, etc., is a clear signal from CGNAT.
Make a traceroute or tracert to your public IP from the command console:

tracert

If there's only one hop, you have a direct public IP. If there are two or more, your connection goes through CGNAT.

If you're having trouble opening ports or hosting services that are accessible from outside your network, this is also a sign of being under CGNAT.
Consult your operatorCall your provider and ask directly if your connection is under CGNAT. Many operators can confirm this and offer options to opt out.

Which operators use CGNAT in Spain?

Currently, the use of CGNAT is quite widespread in the Spanish market, although not all operators apply it in the same way or under the same conditions:

MásMóvil, Yoigo and Pepephone (MásMóvil Group): They use CGNAT by default for new fiber and ADSL subscriptions. They allow you to request a public IP address with just one call to customer service, free of charge in most cases.
Digi: CGNAT applies by default. To obtain a public IP, you must purchase the extra. Plus Connection (currently for 1 euro per month), by calling 1200 from your Digi number or 642 642 642 from another operator.
fine work: CGNAT is mandatory if your connection is on this operator's own network, with no option to disable it. If the network is Vodafone's, this may vary.
Virgin Telco: Uses CGNAT by default, but allows you to request a public IP by contacting customer service (910 053 487).
Movistar, O2 y Vodafone: They don't use CGNAT; all connections have a separate public IP address.
Orange and Jazztel: They use CGNAT only as a gateway between IPv6 and IPv4 clients; it does not affect direct IPv4 clients; they often allow ports to be opened via the PCP protocol, even under CGNAT in some cases.
lowi y SUOP: They do not apply CGNAT to their fiber connections.

Remember that the policy can change over time and depending on the geographic area or the type of access contracted, so it is always advisable to check with the specific operator.

How do I request to leave CGNAT and obtain a public IP address?

If you need to open ports, host a service at home, play online with the lowest ping possible or have advanced home automation, you will surely be interested leave CGNATThe usual procedure is:

Contact customer service from your operator, via phone, web chat or social networks.
Expressly request a public IP and if asked, explain the reason (remote access, servers, games, etc.).
For most carriers, the change is completed within 24-48 hours. You may be asked to restart your router once you receive confirmation.
With operators like Digi, you must subscribe to the “Conexión Plus” service (paid).
Some operators do not allow leaving CGNAT under any circumstances (for example, Finetwork on its own network).

The process is generally quick and there are no penalties, although there may be technical or geographical limitations.

Is CGNAT a security or privacy risk?

An interesting and debated aspect about CGNAT is its influence on security and privacy:

Increases passive safety of your network, since there are no open ports accessible from outside, making direct attacks on your home devices difficult.
On the contrary, it makes it difficult to accurately identify users behind a public IP.Police and law enforcement agencies need special collaboration with operators to link a digital crime to a specific individual when there is CGNAT, which can slow down investigations.
Does not increase privacy risks compared to a traditional public IP, but it exposes you to potential problems if you share an IP with individuals who engage in malicious or prohibited activities.

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Impact of CGNAT on online gaming and the Internet of Things (IoT)

One of the big points of debate is the The effect of CGNAT on online gaming and smart home devices (Internet of Things):

Online games: Most modern games are CGNAT-enabled, but you may notice strict or moderate NAT, increased difficulty when playing on private servers or with advanced settings, and a slight increase in latency. Matchmaking and voice chat may be affected. In highly competitive or older games, a public IP may be essential.
Internet of Things (IoT): If your IoT devices rely on cloud services (most do), you won't have any problems. If you need direct remote control, CGNAT can prevent external communication.

Home automation manufacturers' own cloud platforms have meant that for most users, the presence of CGNAT is no longer an obstacle to managing lights, plugs, cameras, or common virtual assistants.

Does CGNAT affect connection speed?

In general terms, CGNAT does not limit upload or download speeds. from your line, as it only acts on address translation. You can continue browsing, streaming movies, downloading files, or gaming without bandwidth cuts.

However, There may be micro-delays added to the translation process, almost imperceptible, except for very demanding users (professional gamers, high-demand real-time streaming).

What legal or practical problems can CGNAT cause?

Shared bans and restrictions: If someone who shares your public IP address is banned or blocked from a website, you could also be affected.
Tracking illegal activities: Since several people use the same public IP address, the IP address alone isn't enough for the police or a judge to identify the offender; a more in-depth investigation using the operator's logs is required.
Access to security cameras and home servers: If these solutions do not use the cloud and require external access, CGNAT prevents it except in very advanced configurations.

Why isn't it possible to deploy IPv6 en masse and eliminate CGNAT now?

Although IPv6 is the standard that should put an end to CGNAT, the reality is that the world's network infrastructure, operators, and many websites and devices still rely on IPv4. The transition requires multimillion-dollar investments, training of technicians, updating routers and customer systems, and, above all, full network compatibility.

IPv6 brings enormous advantages:

An almost unlimited number of addresses (128 bits compared to 32 for IPv4).
Easier and more efficient automatic configuration.
Native improvements in routing security and efficiency.

But it also brings disadvantages during the transition:

Partial and slow implementation.
Cost of renewing equipment and software.
Need to ensure dual-stack compatibility (IPv4 and IPv6 at the same time) for years.

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Frequently Asked Questions about CGNAT

Can I have a fixed, non-dynamic public IP if I leave CGNAT?
- When you exit CGNAT, your operator usually assigns a dynamic public IP address (it changes with reboots or over time). A fixed public IP address is usually reserved for professional customers or has an additional cost.
Does CGNAT affect my security when banking or shopping online?
- No, encrypted connections using HTTPS and secure authentication systems work the same under CGNAT.
Can I open ports using CGNAT with Orange or Jazztel?
- In some cases, using the PCP protocol is possible, but only for certain ports. Check with your carrier's support team.
How many users typically share a public IP under CGNAT?
- It depends on the operator; at Digi, for example, it can be between 30 and 32 users per shared public IP.
Is CGNAT the same for mobile and fixed connections?
- A form of mass NAT has always existed on mobile devices, but on landlines (ADSL/fiber) it is more restrictive for advanced uses.

Does CGNAT have a future or will it disappear soon?

CGNAT is intended as a transitional solution until IPv6 adoption is widespread and complete. However, the slow migration speed and the need to maintain dual-stack compatibility make it impossible to use it. CGNAT will be present for many years to come in the offerings of the main operators.For more information, you can also consult our article on .

The best way to avoid CGNAT if it is an inconvenience for you is:

Hire operators who do not apply it (Movistar, Vodafone, O2, etc.).
Request a public IP from your current operator if you allow it (MásMóvil, Digi, Virgin Telco, Pepephone, Yoigo, etc.).
Inform you of possible additional costs (as in Digi with Plus Connection).

CGNAT is a key technology in today's connectivity, designed as a temporary solution to the IPv4 shortage and will remain in place until IPv6 is standardized. While for most users it doesn't represent major changes in daily use, it has significant implications for those who require advanced services, online gaming, or remote administration. By understanding its pros and cons, as well as the available alternatives, you can enjoy a connection tailored to your real needs, choosing the best option among operators and managing your public IP request when you deem it necessary.

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