How do I confirm I am actually behind CGNAT?

Compare your router’s WAN address to your public address from an external checker; if WAN is private/shared (for example 100.64.0.0/10) but the public result differs, you are behind CGNAT—use What Is My IP Address to verify.

How can I test whether IPv6 exposure will work for my service?

Ensure your host has a global IPv6, publish an AAAA record, open the port in your firewall, and verify reachability from a network with IPv6 using an online IPv6 Test.

Do I need special DNS changes for VPN port forwarding?

Point your domain to the VPN’s egress host/IP and use a short TTL; verify the AAAA/A records and propagation with a quick DNS Lookup so clients hit the correct endpoint.

Why do certificates fail with HTTP-01 when I only have a random forwarded port?

HTTP-01 requires port 80 on the public host; with random ports you should use DNS-01 validation or a tunnel that terminates TLS at the edge and proxies to you—then check the edge’s address with a simple Reverse DNS Lookup if you need to confirm identity.

What’s the safest way to expose SSH behind CGNAT?

Prefer a reverse tunnel or mesh VPN with key-only auth and allowlisting; if you must use port forwarding, put an SSH bastion on the tunnel host, disable passwords, and throttle logins with fail2ban.

My service is reachable but shows a different country—why?

Traffic exits from your VPN/tunnel provider’s network, so geo-IP reflects their location; if you need to confirm what the world sees, a quick IP Geolocation Map view will show it.

Will WebRTC leak my real IP when I host something through a browser?

Browsers can reveal host candidates via STUN; test and lock down your setup with a WebRTC Leak Test, and consider disabling local candidate exposure if your use case allows.

Does UPnP or NAT-PMP on my router help with CGNAT?

No—those only program your local router; the upstream carrier NAT still blocks unsolicited inbound traffic, so use IPv6, VPN port forwarding, or an outbound tunnel instead.

Bypass CGNAT Safely: IPv6, VPN Port Forwarding, and Tunnels

Carrier-grade NAT squeezes many customers behind a small pool of public IPv4 addresses, which is why your home server, game, or self-hosted app suddenly went dark to the outside world. The good news is you still have safe, reliable ways to accept inbound connections—you just need to route them differently.

Every option below trades off simplicity, security, cost, and speed. We’ll walk through native IPv6 exposure, VPN-based port forwarding, outbound-only tunnels and relays, and when it’s smarter to ask your ISP for a public IPv4. We’ll also call out the failure modes you’re likely to hit and how to test each fix without opening yourself up to random scanners on the internet.

Before you start, sanity-check your goals. Do you need a public endpoint reachable by anyone on the internet (for example a web app or a game server)? Or do you only need private, authenticated access for yourself and teammates? The right answer depends on that line: “public service” points to VPN port forwarding or reverse tunnels with a public hostname; “private access” often points to mesh VPNs with no open ports at all.

Why CGNAT Blocks Inbound Connections

With CGNAT, your router’s WAN interface receives an RFC 1918-style or RFC 6598 shared address (100.64.0.0/10) and the ISP’s carrier router does the public NAT. That means unsolicited inbound packets never reach your router, so traditional port forwarding or UPnP on your own gateway can’t work. Some providers deploy dual-stack transition tech like DS-Lite, lw4o6, or MAP-E/T; these push IPv4 traffic through IPv6 and often remove any possibility of consumer-side inbound IPv4.

Option 1: Go Native with IPv6

If your ISP gives you a global IPv6 prefix (often a /56 or /64), you can expose services natively over IPv6 and skip IPv4 entirely. This restores end-to-end reachability without NAT. The checklist is straightforward: ensure your router delegates IPv6 prefixes to the LAN, assign a global address to your host, open the service in your host firewall (and optionally your router’s IPv6 firewall), publish an AAAA record in DNS, and test from an external IPv6 network.

Pros, Cons, and Safety

Pros: no middleboxes, no extra latency, and clean inbound connectivity. Cons: some clients and networks still lack IPv6; if most of your audience is on IPv4, you may need a dual-stack plan anyway. Safety: because IPv6 is routable end-to-end, lock down the service with TLS, auth, and application-level rate limiting; don’t rely on NAT as a shield. Use minimal open ports, fail2ban-style throttling, and strong credentials/keys.

Option 2: VPN Port Forwarding (Public IPv4 via the VPN)

Several VPN providers still offer inbound port forwarding on selected servers. When enabled, the provider assigns a public IPv4 on the VPN egress plus one or more inbound ports mapped to your VPN session. Your service listens locally; the VPN forwards traffic hitting that public IP:port to your device through the encrypted tunnel. This cleanly bypasses CGNAT because the inbound entry point lives at the VPN provider, not at your ISP.

How to Implement It Safely

Pick a provider that supports port forwarding on your target platform. Enable port forwarding in its app or account portal, then note the assigned port and the VPN egress IP or hostname. Bind your service to all interfaces (or at least the tunnel interface) and verify firewall rules permit traffic from the tunnel to the service. If you need HTTPS, prefer DNS-01 certificate validation or a provider feature that auto-terminates TLS, because HTTP-01 over port 80 is rarely possible on random forwarded ports. For services needing multiple ports (e.g., some multiplayer games), check whether the provider supports ranges; many only forward a single dynamic port.

Pitfalls and Real-World Notes

Not every VPN supports forwarding, and some discontinued it due to abuse. Offerings also vary by region; “works on selected locations” is normal. Expect randomized ports and session-tied mappings that change on reconnect. If your app assumes a stable well-known port, place a TCP/UDP reverse proxy on the tunnel endpoint to remap the forwarded port to the app’s internal port. Finally, watch your provider’s AUP—running public services may be restricted or rate-limited.

Option 3: Outbound-Only Tunnels and Relays

Reverse tunnels avoid any open inbound path by making your machine dial out to a relay you control (or a managed relay), then accepting traffic coming through that established connection. Popular choices include:

Cloud reverse proxies that publish an HTTPS hostname and maintain an outbound tunnel from your host to their edge. These can front HTTP(S), SSH, and more, and remove the need for public ports or public IPs.
Mesh VPNs that auto-traverse NAT and, when direct peer-to-peer fails, transparently relay traffic through provider-operated nodes. Some add a “funnel” mode to publish a web service to the entire internet with automatic TLS.
Self-hosted jump boxes (small VPS) where you run WireGuard/OpenVPN and optionally a reverse proxy. Your CGNAT-bound host connects outbound to the VPS; the VPS holds the public IP and handles inbound.

Security Model and Tradeoffs

These systems usually authenticate at the edge and may terminate TLS there, so review how identities, keys, and certificates are issued and rotated. Performance depends on whether peers can go direct; if they fall back to a relay, expect extra latency and lower throughput. On the plus side, setup is fast, and the “no inbound on your WAN” posture is inherently safer for home networks.

Option 4: Ask Your ISP for a Public IPv4 or Static IP

Some ISPs sell a public (sometimes static) IPv4 add-on or a business tier that lifts CGNAT. This is the most straightforward fix if you run multiple public services, need standard ports, or want full control over DNS and certificates with HTTP-01. The downsides are monthly cost and a larger attack surface—you’ll be responsible for hardening and monitoring an internet-facing network edge.

What Not to Do

UPnP/NAT-PMP on your home router won’t pierce CGNAT, because the real NAT is upstream. Port-control protocols like PCP only work if the carrier’s CGN devices expose and honor them for end customers, which is rare. Randomly changing router settings, enabling DMZ, or disabling firewalls won’t help and can make things worse.

Testing and Hardening Checklist

Verify exposure from outside your network, not from another device on the same LAN or over the same tunnel. Confirm which IP and port the world sees—VPN egress for forwarding, provider edge for tunnels, or your native IPv6 for AAAA. For web services, force HTTPS, use modern ciphers, and prefer DNS-01 for certificates in forwarded/tunnel setups. For SSH, disable password logins and use keys with rate limiting. For WireGuard or similar, set reasonable keepalives on NATed nodes to maintain mappings and monitor logs for handshake stability. Always scope firewall rules to the minimum ports needed and apply application-level auth whenever possible.

Monitoring and Certificate Renewal

Automate certificate issuance and renewal with DNS-01 where possible, keep DNS TTLs short during migrations, and watch logs at the edge proxy for 4xx/5xx spikes that hint at misrouted tunnels or expired certs. If your provider rotates egress IPs, pin by hostname and use health checks that verify both TLS validity and application responses, not just port openness.

Choosing the Right Path

If your audience can reach you over IPv6, enabling native IPv6 is the cleanest fix. If you need public IPv4 reachability with minimal fuss, a VPN that supports port forwarding is practical and keeps your real WAN hidden. If you only need private access or want quick HTTPS sharing without managing certificates, an outbound tunnel or mesh VPN “funnel” is ideal. If you’re running multiple services for many users, paying your ISP for a public/static IPv4 may be simpler in the long run.

A Minimal Decision Tree

Can your users reach IPv6? If yes, publish AAAA and secure the app. If no, do you need open access for the whole internet? If yes, pick VPN forwarding or a reverse tunnel with a public hostname. If no, use a mesh VPN that gives device-to-device access without open ports. When in doubt, start with the tunnel/mesh option; you can always graduate to public IPv4 later if your use case grows.

Operational Tips That Usually Save Time

Separate “edge” and “app” duties: let the tunnel/VPN host run a tiny reverse proxy and keep your app on another port or container. Put logs and metrics at the edge so you can tell direct vs relay traffic at a glance. Keep DNS low-TTL while experimenting. And document your port/host mappings—forwarded ports change more often than you think.