HTTPS Reverse Proxy on IIS 10 – External Access Fails (Timeout) Although Local Requests Work

Hello everyone,

I’m currently facing an issue with an IIS 10 reverse proxy configuration on Windows Server, and I would really appreciate your guidance.

Environment

Windows Server

IIS 10

Application Request Routing (ARR) + URL Rewrite enabled

Backend application running on:

http://localhost:8080/ http://localhost:8080/login

Public domain:

https://lojistik.abc.com.tr

What I want to achieve

I want users to access the backend web application through the following URL:

https://lojistik.abc.com.tr/LMYS/login

Internally, IIS should proxy this to:

http://localhost:8080/login

What works

The backend application is accessible without issues:

http://localhost:8080/login

From the server itself, reverse proxy works:

Invoke-WebRequest "https://lojistik.abc.com.tr/LMYS/login"

→ StatusCode: 200 (success)

What does NOT work

From any client machine, the following request results in a timeout:

https://lojistik.abc.com.tr/LMYS/login

Browser shows connection timeout.

No entry appears in IIS logs for external requests to /LMYS/....

Tests performed

▪ netstat -ano | findstr :443 on the server → Port 443 is listening ▪ DNS resolves correctly:

lojistik.abc.com.tr → 10.6.130.90

▪ Reverse proxy rule on IIS is correctly configured under the HTTPS binding site:

Pattern: ^LMYS(/.*)?$ Rewrite to: http://localhost:8080{R:1}

▪ ARR Server Proxy is enabled.

Key observation

Requests from the server itself succeed (reverse proxy returns 200), but external clients always time out, which suggests that the HTTPS traffic is not reaching IIS at all (likely blocked or not NAT-forwarded on the network path).

Question

What could cause HTTPS (port 443) traffic to reach IIS locally, but external requests to the same port to hang indefinitely?

Any guidance would be greatly appreciated.

Thank you in advance.

Best regards,