Why can't I port forward?
Why can't I port forward?
Long ago I used a spectrum device with their modem/router combo at 200/10mbps and port forwarding worked. After relocating to a larger city, I switched to Google Fiber and consulted two different support teams at Google. They kept pointing out whether the issue was with the ISP (Google Fiber) or the router. A year later, I moved again and got a Spectrum unit for port forwarding. However, ATT became my next option. Research showed that the modem/router combo isn’t suitable for port forwarding, and there’s no extra fee for free modems. Still, I couldn’t get it to work despite correct firewall settings, router configuration, DHCP reservation, and static IP setup. Ports remained closed. I checked online forums and saw most advice suggested the problem was with the Spectrum device itself—locked down and lacking a user interface. Even when using my Asus RT N66R with the default Spectrum modem, it kept saying the ISP’s DHCP wasn’t set right. Eventually, I bought a Netgear CM600 modem, and the Asus router functioned properly after port forwarding. Now I have a static IP and ports are open. I reached out to Spectrum tech support via text, but they insisted it was the router issue and gave me a 28-minute explanation: “It’s the router—it’s not on Spectrum’s end.” Despite everything being set up correctly on my side, changing ISPs, devices, or PCs didn’t resolve the problem. Anyone have any ideas?
I checked whether the port is accessible using the router’s WebUI. Make sure everything is set up properly. Typical problems involve Double NAT or NAT64-CGNAT issues, but a coax network from Spectrum usually avoids those. I’ve also heard concerns about fiber networks, though results can vary by location. It’s important to confirm your public IP is in the Public Domain and isn’t reserved for NAT. Keep in mind that an online port checker only confirms openness if a server is running on that port; otherwise it might mislead you. In extreme cases, you could set up a VPS and bypass the restriction. Just install VPN hosting software on the VPS and connect—done.
Focused on portcheckers community, but also receives messages from friends through cmd. Uncertain about whether the IP is public or reserved. It appears when I set up a server and discuss VPS and VPN, a friend can connect via VPN because port forwarding functions for him—would this apply to you?
Spectrum handles CG-NAT correctly. Begin the Minecraft server using its local IP address; this allows port forwarding from your public IP to the internal one. It’s not attempting to connect to your public IP, which you probably don’t want.
They confirmed the site existed and denied ignoring it. I resolved the issue, and the server is now running. By the way, my public IP keeps shifting—no idea how to fix that either.
I noticed you discovered the answer to your concern. That’s encouraging. In cases where CGNAT was the problem, it could have been effective, but as Lurick pointed out, I can confirm Spectrum typically doesn’t rely on CG-NAT. Based on my understanding, if the server runs on an active VPN, that makes a lot of sense. You should disable it or use a different setup to host the server separately from the VPN systems you wish to manage.