The solution is quite simple.
I expect you have already port forwarded the WAN Address with the Port, for example 443 (https), to your Webservers LAN or DMZ IP-Address. if not you wouldnt reach your Server from www.
If you want to connect to your Webserver Via local net and with the domainname, for example "cloud.mydomain.com" you have to set a second portforward from your LAN to your LAN or from your LAN to your DMZ.
For Example
- Interface: LAN
- Target: WAN IP-Address (your static WAN IP on which your DNS is routed to.)
- To Target: local IP-Adress of your Webserver
- From Port: 443
- To Port: 4443 (i never make from/to ports the same, my Server is listening local on 4443)
Example with OpnSense (my favorite firewall/router)
