What Is CGNAT? How Carrier-Grade NAT Makes Mobile Proxies Unblockable

Mobile proxies are considered the most trusted proxy type available. They are rarely blocked, almost never blacklisted, and enjoy the highest trust scores on virtually every major website. The reason has everything to do with a technology called CGNAT — Carrier-Grade Network Address Translation.

Understanding CGNAT explains why mobile proxy IPs are shared by thousands of legitimate users, and why websites simply cannot block them without causing massive collateral damage.

What Is CGNAT?

CGNAT (Carrier-Grade NAT), also known as Large-Scale NAT (LSN) or CGN, is a Network Address Translation technique used by Internet Service Providers (ISPs) — particularly mobile carriers — to share a single public IPv4 address among hundreds or thousands of subscribers.

The Problem CGNAT Solves

There are only 4.3 billion IPv4 addresses. With over 8 billion people on the planet and multiple devices per person, ISPs cannot assign a unique public IPv4 address to every subscriber. Mobile carriers, which have added billions of subscribers over the past two decades, face the worst of this shortage.

CGNAT solves this by placing a NAT (Network Address Translation) device at the carrier level, mapping many private subscriber connections to a smaller pool of public IP addresses.

How CGNAT Works

Subscriber A (Phone) --\
                        \    +-------------------+     +-----------+
Subscriber B (Phone) ------>|   CGNAT Device     |---->| Internet  |
                        /   | (Carrier Network)  |     | (Public)  |
Subscriber C (Phone) --/   |                     |     |           |
       ...                  | Maps thousands of   |     |           |
Subscriber N (Phone) ----->| private IPs to a    |     |           |
                           | pool of public IPs  |     |           |
                           +-------------------+      +-----------+

Private IPs (10.x.x.x)     Public IP pool           Target websites see
assigned to each phone      (e.g., 50 public IPs    the shared public IP
                            shared by 50,000 users)

Here is the step-by-step process:

Your phone gets a private IP address from the carrier (e.g., 10.45.23.107).
You browse the web. Your request goes to the carrier’s CGNAT device.
The CGNAT device translates your private IP to one of its pool of public IPs (e.g., 185.23.67.89).
The destination website sees the request coming from 185.23.67.89.
Thousands of other subscribers are also being translated to that same public IP at the same time.

The website sees one IP address. Behind that IP, there are potentially thousands of real human users.

Why CGNAT Makes Mobile Proxies Unblockable

This is the critical insight that makes mobile proxies so effective. Here’s the logic:

The Blocking Dilemma

When a website detects suspicious activity from an IP address, the standard response is to block or rate-limit that IP. This works well for:

Datacenter IPs: Blocking a datacenter IP affects only the proxy user.
Residential IPs: Blocking a residential IP affects one household (typically 1-10 users).
Mobile/CGNAT IPs: Blocking a CGNAT IP affects thousands to hundreds of thousands of legitimate users.

If Google blocked a single CGNAT IP used by a mobile carrier, they could be blocking access for 50,000 real smartphone users in a major city. If Instagram blocked that IP, tens of thousands of legitimate users would lose access.

Real-World Numbers

To illustrate the scale:

A major carrier in a city of 5 million people might use as few as 500-1,000 public IPv4 addresses for mobile subscribers.
Each public IP could have 5,000-50,000 active subscribers behind it at any given time.
During peak hours, a single CGNAT IP might serve over 100,000 concurrent connections from different users.

Blocking one CGNAT IP = blocking tens of thousands of paying customers.

No major website is willing to do this. The collateral damage is simply too great. This is why mobile proxy IPs enjoy the highest trust level on the internet.

How Websites Handle CGNAT Traffic Instead

Since outright blocking is not an option, websites use softer measures for suspicious CGNAT traffic:

CAPTCHAs: Presenting a CAPTCHA challenge instead of blocking.
Rate limiting per session: Limiting request rates per browser session rather than per IP.
Behavioral analysis: Examining user behavior patterns rather than IP reputation.
Device fingerprinting: Identifying individual devices behind the shared IP.
Cookie tracking: Using cookies to track individual users regardless of shared IP.

These measures target the specific suspicious user without affecting the thousands of legitimate users sharing the same IP.

CGNAT Adoption by Country

CGNAT adoption varies significantly by country and is driven by IPv4 address scarcity and mobile subscriber growth:

Country/Region	CGNAT Adoption	Notes
India	Very High	Massive mobile user base, limited IPv4 allocations
Southeast Asia	Very High	Rapid mobile growth, late-stage IPv4 allocation
China	High	Huge subscriber base, extensive CGNAT deployment
Brazil	High	Large population, mobile-first internet access
Africa	High	Mobile-primary internet, limited IPv4 infrastructure
Europe	Moderate	Better IPv4 allocations, faster IPv6 adoption
United States	Moderate	Major carriers use CGNAT for mobile; some offer public IPs
Japan	Moderate	Early IPv6 adoption reduces CGNAT pressure

Countries with high CGNAT adoption tend to produce mobile proxy IPs with the highest trust scores, because each IP is genuinely shared by the largest number of real users.

CGNAT and IPv6: The Long-Term Picture

CGNAT is fundamentally a workaround for IPv4 scarcity. IPv6, with its virtually unlimited address space, eliminates the need for CGNAT entirely. In an IPv6 world, every device can have its own unique public address.

However, the transition to IPv6 is slow:

Many websites still only accept IPv4 connections.
Legacy infrastructure doesn’t support IPv6.
Dual-stack (supporting both IPv4 and IPv6) is the transition strategy, meaning CGNAT remains necessary for IPv4 traffic.

For the foreseeable future, CGNAT will continue to be the backbone of mobile carrier networking, and mobile proxies will continue to benefit from the trust inherent in shared CGNAT IPs.

How Mobile Proxies Leverage CGNAT

Mobile proxy providers connect devices (SIM cards in modems, phones, or dedicated hardware) to mobile carrier networks. When you use a mobile proxy:

Your Computer/Server
        |
        | Request via proxy gateway
        v
+---------------------+
| Mobile Proxy Device |  <-- Connected to carrier via 4G/5G SIM
| (SIM card + modem)  |
+---------------------+
        |
        | Traffic goes through carrier network
        v
+---------------------+
| Carrier CGNAT       |  <-- Assigns shared public IP
+---------------------+
        |
        | Request from CGNAT IP (shared with thousands of real users)
        v
Target Website

The target website sees the same type of IP address that thousands of legitimate mobile users in that area are currently using. The traffic is indistinguishable from a regular person browsing on their phone.

IP Rotation in Mobile Proxies

Mobile proxy providers can trigger IP rotation by:

Toggling airplane mode: Disconnecting and reconnecting to the carrier reassigns a new CGNAT IP from the carrier’s pool.
Network reset: Resetting the mobile data connection forces a new IP assignment.
Timed rotation: Automatically cycling the connection at set intervals.

Each new IP comes from the same carrier’s CGNAT pool and carries the same high trust level.

Practical Implications for Proxy Users

Why Mobile Proxies Cost More

Mobile proxies are the most expensive proxy type (typically $15-30/GB or $50-300/month per IP) because:

Physical hardware (SIM cards, modems) is required.
Each device requires a mobile data plan.
Bandwidth is limited by cellular network speeds.
Infrastructure management is complex.

The premium price reflects the premium trust level that CGNAT IPs provide.

Best Use Cases for CGNAT-Backed Mobile Proxies

Mobile proxies excel where trust is paramount:

Social media account management: Platforms like Instagram, TikTok, and Facebook heavily scrutinize IP addresses. CGNAT mobile IPs pass these checks. See our social media proxy guide.
Ad verification: Verifying ads as they appear to real mobile users.
Account creation: Creating accounts on platforms that block datacenter and flagged residential IPs.
Sensitive scraping: Scraping targets with aggressive anti-bot measures. See our web scraping proxy guide.

Checking Your CGNAT IP

Use our IP Lookup Tool to check:

Whether your IP is classified as mobile/carrier.
The ISP/carrier associated with the IP.
The geographic location assigned to the IP.
Whether the IP is flagged in any blacklist databases.

A properly functioning mobile proxy should show a carrier name (e.g., T-Mobile, Vodafone, Airtel) and classify as mobile/cellular.

Frequently Asked Questions About CGNAT

Does CGNAT Affect Internet Speed?

CGNAT adds a small amount of latency (typically 1-5ms) due to the additional NAT translation. For most users this is imperceptible. However, CGNAT can cause issues with certain applications that require direct inbound connections, such as peer-to-peer services, online gaming hosting, and some VoIP configurations. These applications may need NAT traversal techniques (STUN, TURN) to function properly behind CGNAT.

Can I Tell If I’m Behind CGNAT?

Yes. If your device’s local IP address is in the 100.64.0.0/10 range (100.64.0.0 to 100.127.255.255), you’re behind CGNAT. This range is specifically reserved for carrier-grade NAT (RFC 6598). You can also compare your device’s IP with your public IP — if they differ and you’re not on a home Wi-Fi router doing NAT, you’re likely behind CGNAT.

Is CGNAT the Same as Double NAT?

Similar but not identical. Double NAT occurs when your traffic passes through two NAT devices (e.g., your home router and your ISP’s CGNAT). CGNAT is one layer of that double NAT — the ISP-level layer. The practical effect is the same: your traffic undergoes two address translations before reaching the public internet, and inbound connections become more difficult.

Why Don’t All ISPs Use CGNAT?

Some ISPs, particularly legacy providers with large IPv4 allocations from the early days of the internet, still have enough IPv4 addresses to assign one to each subscriber. Wired broadband providers are more likely to offer public IPv4 addresses than mobile carriers, because mobile subscriber growth has been much more explosive. Additionally, some business-tier ISP plans guarantee a public IPv4 address as a feature.

CGNAT Detection: Can Websites Tell?

Websites can sometimes detect that an IP is behind CGNAT, but this doesn’t help them block it:

Port range analysis: CGNAT devices often assign specific port ranges to different subscribers. Unusual port numbers can indicate CGNAT.
Connection volume: An IP with an unusually high number of concurrent connections may be identified as CGNAT.
Carrier IP range databases: IP intelligence databases classify IP ranges by their assignment (residential, mobile, datacenter).

The detection doesn’t matter because the conclusion is the same: blocking the IP would affect too many real users. Detection of CGNAT is actually a signal that the IP is legitimate and should be treated carefully.

Conclusion

CGNAT is the technology that makes mobile proxies the most trusted and hardest-to-block proxy type available. By sharing a single public IPv4 address among thousands of real mobile subscribers, CGNAT creates a situation where blocking proxy traffic means blocking real customers. No website is willing to take that risk, which is why mobile proxy IPs consistently achieve the highest trust scores across every major platform.

For more on proxy types and how they work, visit our proxy glossary.