TL;DR

CGNAT (Carrier-Grade NAT) blocks inbound connections by placing multiple households behind a single shared public IP, making traditional port forwarding ineffective since you can’t configure rules on the infrastructure your ISP controls.

Reverse tunnels solve this by flipping the connection model: your device initiates an outbound connection to a public relay server, which then brokers remote access without ever requiring an open inbound port, public IP, or router access.

Who needs this: home lab users, MSPs, IoT/edge deployments, and developers who can’t guarantee network control at every site.

What to look for in a solution: always-on persistence, simple deployment, and built-in hostname/DNS management.

No-IP Public Tunnels delivers a production-ready implementation that is encrypted, outbound-only tunnels that work reliably across any network, with no ISP coordination required.

What Is CGNAT?

Before exploring the solution, it helps to understand the problem.

CGNAT is a practice used by Internet Service Providers (ISPs) to conserve IPv4 addresses. With the global inventory of IPv4 addresses running low, ISPs can no longer assign a unique public IP to every subscriber. Instead, they group many customers behind a single shared public IP address using NAT at the carrier level.

If you already know how NAT works on your home router, where your router assigns private IPs to devices on your local network and uses one public IP to communicate with the internet, then CGNAT is essentially that same concept applied one layer higher. Your entire household might share a public IP with dozens or even hundreds of other households on your ISP’s network.

This is invisible to most users. You can still load websites, stream video, and use apps without any issues. However, the moment you need remote access to reach into your network, such as a security camera, a self-hosted service, or a remote desktop connection, CGNAT becomes an impenetrable wall.

Why Carrier-Grade NAT Prevents Inbound Connections Without Port Forwarding

Port forwarding allows you to gain access through your router’s NAT, directing incoming traffic on a specific port to a specific device inside your network.

With CGNAT, you don’t control the outermost layer of NAT. Instead, your ISP manages it. That means:

• You don’t have a unique public IP address. The IP that external services see belongs to your ISP, not you. It’s shared across many subscribers.
• Port forwarding only works on hardware you control. Even if you forward a port on your home router, that traffic still hits a dead end at the ISP’s CGNAT layer.
• The ISP won’t configure rules on your behalf. Consumer ISPs don’t offer customers the ability to modify their CGNAT platform.

Therefore, CGNAT prevents port forwarding from making a remote access connection.

Increasingly, this is the reality for home users on cable or fiber ISPs, for devices deployed at customer sites by MSPs, and for IoT or industrial hardware sitting behind ISP-managed routers.

How Reverse Tunnels Work and Why They Bypass CGNAT

A reverse tunnel flips the connection model. Instead of waiting for an inbound connection to arrive at your device, which CGNAT blocks, your device reaches outward to establish a connection to a relay server on the public internet. That relay server then brokers access requests from the other direction. In other words, instead of an external user reaching out to your network and awaiting access, the device inside your network reaches outward and establishes a persistent connection to an external relay server.

Here’s the key insight: outbound connections are rarely blocked by CGNAT. The ISP’s NAT allows devices behind it to initiate connections outward freely. A reverse tunnel takes advantage of this by:

1. Your device (behind CGNAT) initiates an outbound, encrypted connection to a publicly accessible relay server.
2. The relay server maintains that persistent connection, associating it with a hostname or URL.
3. When someone wants to access your device, they connect to the relay server.
4. The relay forwards that traffic through the existing outbound tunnel and does not require an inbound port or public IP.

From the CGNAT platform’s perspective, all it sees is the outbound connection your device made. No rules need to change or ISP cooperation is required. The CGNAT layer is bypassed completely because it was never asked to allow inbound traffic in the first place.

Reverse Tunnels vs. Port Forwarding: A Practical Comparison

If you have a public IP, full router access, and a controlled network environment, port forwarding may still be a fine choice. But for any deployment where those conditions aren’t guaranteed, a reverse tunnel is the more resilient architecture.

Who Needs a Reverse Tunnel?

The short answer: anyone who has struggled with inbound connectivity and doesn’t have guaranteed control over the network they’re on.

Home lab users are among the most common victims of CGNAT. If you’re self-hosting services or running a home automation setup, but can’t get inbound connections to work, CGNAT is the likely culprit.

MSPs and IT teams supporting customer environments face CGNAT constantly. Customer sites often run on consumer-grade ISP connections with no dedicated IP and no router access available. A reverse tunnel lets the team maintain reliable remote access without coordinating network changes with the customer or the ISP.

IoT and edge device deployments, such as security cameras, industrial sensors, or remote hardware, may be installed on networks that are completely outside the deployer’s administrative control. Reverse tunnels are often the only workable remote access method in these environments.

Developers and small businesses exposing internal services, webhooks, or staging environments will hit CGNAT-related issues if they’re not on a dedicated-IP plan.

What to Look for in a Reverse Tunnel Solution

Not all reverse tunnel implementations are equal. When evaluating options, there are a few factors to take into consideration:

Persistence. Some tunneling tools are designed for short-lived developer sessions. They involve spinning up a URL, testing a webhook, and closing it. That’s useful for some configurations, but doesn’t support remote access needs. Look for solutions designed for always-on access.

Ease of deployment. If setting up the tunnel requires deep networking knowledge or extensive configuration, it may create overhead friction. A more compatible solution would lean away from NAT traversal, IP management, and firewall behavior so that access just works.

Domain and URL management. Built-in support for custom hostnames tied to a Dynamic DNS or managed DNS platform adds meaningful flexibility.

A Solution Built for CGNAT Realities

The networking landscape has shifted. CGNAT is no longer a one-off case. Instead, it’s the means of connection for a growing portion of consumers and small business ISP connections. Remote access solutions that depend on inbound connectivity and router-level configuration don’t always apply, depending on the user’s needs.

Reverse tunnels represent a fundamentally more compatible model for this environment. By initiating connections outbound, they sidestep the CGNAT problem entirely without requiring any special ISP arrangements, unique public IPs, or firewall exceptions.

If you’re looking for a production-ready implementation of this approach, No-IP Public Tunnels is a modern remote access solution built specifically for environments where traditional port forwarding fails. It uses outbound-only encrypted tunnels to provide consistent, secure access across any network, CGNAT or otherwise, accessible through simple, shareable URLs. It’s designed not just for developers, but for IT teams, MSPs, and businesses that need remote access to work reliably everywhere, every time.

No-IP Public Tunnels is launching SOON! Learn how to get early access and be among the first to adopt this modern remote access solution.