When I turn on under attack mode, some of my subdomains go offline

My main domain is getting hammered, so I turned on Under Attack Mode. After I did that, some but not all, of my subdomains became unreachable.
example.com Under Attack Mode on
test.example.com unreachable
bork.example.com unreachable
temp.example.com is ok

How do I prevent the subdomains from being unreachable?

You can use Configuration Rules to set the security level based on host (or other parameters)…


  • turn off UAM globally and set it for the domain; or
  • turn on UAM globally and set another level for each subdomain

You probably need to find the root cause why the subdomains are unavailable. Check that your origin is still capable of servicing requests for them.

Thanks for the quick reply. Agreed that I need to find out why some subdomains work and others don’t. Please excuse my ignorance, but what do you mean by “checking origin is still capable of servicing requests”?

If you are under attack, see how many requests are making it through to your origin and what load it is under. They may be coming through subdomains that aren’t set for UAM, or directly to your origin IP address and not through Cloudflare.

If your origin is working ok, then you need to find out the root cause of why the subdomains don’t work. See if your own requests are being blocked by UAM.