Cloudflare proxy stops AWS network load balancer working

Hi guys,

I have a Fargate task connected to an AWS Network Load Balancer. I have made the task security group maximally permissive with cidr_blocks = [""]. I can point a CNAME record to NLB and with DNS-only I can connect to my task no problem. However, when I turn on proxying I fail to be able to connect. I could understand why this might not work if I had more restrictive CIDR blocks which did not include the Cloudflare proxy servers, however with all IPs allowed I am not sure why this stops the connection working.

Does anybody have any pointers?

Are you connecting on some specific, non standard ports?

Port 8000

That’d be the issue. Cloudflare doesn’t support port 8000.

Yep that was it, thanks!

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