Solved Admin Console from LAN using FQDN (Split DNS)

[ois]

I am having an issue connecting to the admin console from my LAN using the FQDN. I have split dns setup and it has been working for quite some time. It seems to have stopped working after a recent round of updates to Windows and 3CX. When connecting to admin console from LAN computers I get "ERR_CONNECTION_REFUSED"

3CX is running on a Virtual Windows Server 2016 on Hyper-V

Admin Console works:

- On 3CX server where XXX.md.3cx.us resolves to 127.0.0.1

- From outside network where XXX.md.3cx.us resolved to public IP address

- From LAN computers when using the IP address of 3CX server (I.E. https://10.10.10.220:5001)

Does NOT work from LAN computers using FQDN (I.E. https://XXX.md.3cx.us:5001 )

I verified that split dns is working and the LAN computers do resolve XXX.md.3cx.us to 10.10.10.220.

I have tried turning off the windows firewall completely on the 3CX server and still get ERR_CONNECTION_REFUSED.

Any suggestions would be appreciated. Thanks in advance.

 

[SteveITS]

Just a guess but ensure your browser isn't using DoH (DNS over HTTPS). Are you sure your PC's IP isn't blacklisted?

 

[ois]

Just a guess but ensure your browser isn't using DoH (DNS over HTTPS). Are you sure your PC's IP isn't blacklisted?

Awesome. Looks like it was DNS over HTTPS. I disabled it and it works. I will test on other LAN computers as well. Thank you VERY much.

 

[SteveITS]

That's the down side to it...it completely bypasses local DNS. (filtering, security, split DNS, etc.)