I cannot access subdomain hosted externally from LAN

dns-zonesubdomainwindows-server-2012-r2

MY QUESTION:
I want to run a web application on sub-domain subdomain.example.com. Sub-domain is created by ISP on their DNS server and forwarded to external web host. None of clients can access the sub-domain from within LAN. It works outside of LAN, even on different ISP. I am using Windows 2012 R2 domain controller. Router has port 80 open.

Tried:

  • Created A record on local DNS with IP of my ISP DNS server.
  • Outbound access from firewall is not restricted.
  • Created separate zone on local DNS with A record pointing to ISP DNS server.

What am I missing? I am thoroughly lost.

Best Answer

It sounds like you're running into an issue requiring NAT Loopback to be enabled on your router. From Wikipedia:

NAT loopback, also known as NAT hairpinning or NAT reflection,[6] is a feature in many consumer routers[7] which allows a user to connect to his/her own public IP address from inside the LAN. This is especially useful when, for example, a website is hosted at that IP address.

Look for options in the documentation for your router to enable NAT loopback - once enabled, as above, you should find that clients on the LAN are able to access the web server using the FQDN which resolves to the public IP of the router which then in turn forwards port 80 to the web server.

EDIT:

It looks like you've substantially changed your question to change its overall meaning, which is somewhat confusing. In any case - the A record(s) you've created for the subdomain in question should point at the IP of the webserver you want to access - not the DNS servers of the ISP.

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