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I'm facing a bizarre issue where all devices on my home network that try to access a locally-hosted, publicly accessible website via its public IP / domain are timing out, but it works fine using the private IP, or when accessing it through a VPN or external network, or by using a port other than 80.

This is a recent phenomenon, and has been working for months prior. The particular website I'm testing with is simple HTML, so no server-side code that might cause problems for certain IPs.

Example:

| URL                     | Works on devices using same network as server | Works on devices using external network / VPN 
| ----------------------- |---------------------------------------------- | ---------------------------------------------
| http://[my-website].com | No                                            | Yes                                           
| http://[public-IP]      | No                                            | Yes                                          
| http://[public-IP]:8085 | Yes                                           | Yes              
| http://[private-IP]     | Yes                                           | Yes
| http://[private_IP:8085 | Yes                                           | Yes

The server is Windows 10 using IIS 10.0. I currently have the "default website" bound to both 80 and 8085 to recreate the issue. It works fine on every device I try except for ones inside the network using port 80.

I've tried the following:

  • Disabling firewall
  • Disabling proxy settings
  • Using different DNS servers
  • Flushing/renewing DNS
  • Verifying hosts file has no entries
  • Clearing browser cache
  • Using different browsers
  • Restarting web server
  • Restarting router

Does anyone have any idea what could be causing this, or how I could troubleshoot this further?

EDIT: I'm thinking I may need to contact Comcast since it's their router, and since I haven't changed anything with my web configuration, maybe it's a problem with the firmware or something?

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  • Are you actually using IIS? If that is indeed the case tell us more about that configuration by editing your question.
    – Ramhound
    Commented May 12, 2022 at 3:21
  • The problem being limited to port 80 complicates things, but overall this still sounds to me like another "NAT hairpin" / "NAT loopback" issue that we've had many times in the past. (If [public_ip] belongs to your router, then sometimes port 80 has special handling because that's how you (or they) access the router's web management UI.)
    – grawity_u1686
    Commented May 12, 2022 at 4:30

1 Answer 1

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In case anyone encounters this in the future, I bought a new router, switched the Comcast Gateway I'm using into bridge mode (i.e. turned off all router functions so it operates solely as a modem), and the problem instantly resolved itself. So it was likely a firmware issue with Comcast's router.

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