A Record (Cloudflare) pointing to EC2 instance not reachable

Question

I have a subdomain that I want to point my EC2 instance. My instance is running a 3rd party software that requires HTTPS. I use Cloudflare for all my DNS routing and created an A Record to point to my EC2 IP address. I have no problems access it by IP, but fails when using the subdomain address (test.mydomain.com). Receiving an Error 520 message - Web server is returning an unknown error. I made sure that:

EC2 security group port 80/443 is open for both 0.0.0.0/0 and ::/0
Cloudflare SSL/TLS is set at Flexible

Not sure what I'm missing?

* EC2 security group port 80/443 is open for both 0.0.0.0/0 and ::/0
* Cloudflare SSL/TLS is set at Flexible

Not sure what I'm missing?

Answer

Another troubleshooting step: Edit the hosts file on your PC and add `test.mydomain.com` as an entry with the IP address of your instance. Then you will be able to see what the instance is returning. You can also do this with tools like `curl` and `wget` by setting the `Host` header in the request.

Answer

Hi.

Are you hosting a web server on EC2?  
You should check the access log and error log of the web server. Then you should find the reason why Cloudflare responds with 520 error.

A Record (Cloudflare) pointing to EC2 instance not reachable

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