I have an elastic load balancer in an AWS VPC.

I can access the resources successfully behind the load balancer exposed on different ports - standard https 443 and a couple of higher ones say 8888.



all work - I get the expected security warning but can ignore and access the service.

I then added a CNAME record for mysite.example.com to point at https://aws-elb.xxxxxxxxxxxx.region.com and got a cert for mysite.example.com.

Now I can access


successfully, but


times out.

I was under the impression that the CNAME would just route through to the underlying url and all would work?


That's weird, DNS has nothing to do with the port you're connecting to (443, 8888).

Are you sure you're testing it from the same place? Does the ELB security group permit connection to 8888 from your location?

Or is it perhaps not timeout but instead some other error that you're facing on 8888?

  • Turns out the dns provider only proxy a couple of non standard ports. The request was never making its way to the elb (found that it by turning on the logging and seeing only 443 was getting hit). – PaulB Mar 18 '19 at 6:25
  • @PaulB DNS translates host names to IP addresses, nothing else. It’s got nothing to do with ports. Really. From your location try the ALB address on port 8888 and the hostname on port 8888 and see what it does. Even if there is a problem it’s got nothing to do with DNS. – MLu Mar 18 '19 at 7:19
  • @PaulB Like I said - it’s got nothing to do with DNS and everything to do with CloudFlare port forwarding ;) It would have been useful if you had mentioned that you’re using CloudFlare as that’s a whole extra layer between your clients and your site. – MLu Mar 18 '19 at 7:37
  • Appreciate your help ... I had no idea a CNAME had anything to do with port forwarding ... thought it was just an alias to url - hence no mention of Cloudflare. – PaulB Mar 18 '19 at 15:17

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