I manage a small business website that suddenly stopped being accessible for users on the AT&T cellular network. When I try to connect using my AT&T phone, it seems like the connection is being dropped. However, I can access the site when I use a VPN or connect through WiFi. I ran some tests and confirmed that when using the cell network, DNS resolution works properly (I can resolve the host) and I'm able to SSH into the server via its IP address.
I tried using various trace tools through a hotspot, but they filtered UDP packets so heavily that they were of no use. All my TLS checks indicate that the website is functioning normally, and it doesn't appear to be blacklisted. We're feeling pretty stuck here—any ideas on what might be causing this issue?
Update: I discovered that my server was rejecting all IPv6 connections due to an issue in my Nginx configuration. Initially, I only had `listen 80;`, but I needed to add `listen [::]:80;` to resolve the problem. This issue seemed to have arisen only recently despite my setup being fine for years.
5 Answers
Using a hotspot could help you troubleshoot better. Try connecting over HTTP instead of HTTPS, and check any subdomains you might have. This might give you a clearer picture of what’s happening.
I experienced something similar recently. Even though I was on a dedicated IP, it was still flagged, affecting accessibility across some networks. Verify your server's IP against spam lists to see if there are any issues.
I suspect this could partially be an IPv6 issue. If your server isn’t set up to handle IPv6 requests, it might be causing problems for users who are generally assigned IPv6 addresses by mobile carriers like AT&T. Make sure your server configuration accommodates both IPv4 and IPv6.
Make sure to check if your site is listed on any spam or malware blacklists used by AT&T. You mentioned it’s not flagged, but it’s worth double-checking. Sometimes, even if it’s not showing obvious flags, there could be hidden issues.
It sounds like a DNS problem on AT&T's end. Since you can access your site directly through the IP address, this likely means DNS resolution is failing for your domain. ISPs often cache IP addresses, and it’s possible yours is pointing to an outdated one. You might want to check if the lease time is set correctly for your domain, as a short lease time could lead to issues if the IP changes frequently.
Related Questions
Cloudflare Origin SSL Certificate Setup Guide
How To Effectively Monetize A Site With Ads