A Record (Cloudflare) pointing to EC2 instance not reachable


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 and ::/0
  • Cloudflare SSL/TLS is set at Flexible

Not sure what I'm missing?

asked 2 years ago1051 views
2 Answers


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.

profile picture
answered 2 years ago

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.

profile pictureAWS
answered 2 years ago

You are not logged in. Log in to post an answer.

A good answer clearly answers the question and provides constructive feedback and encourages professional growth in the question asker.

Guidelines for Answering Questions