HOWTO create subdomain pointing to external server, if even possible

So here is what I was thinking of..
I am pooking around with HomeAssistant to get a smart house, I have a domain and that is working fine on ISPConfig like mydomain.com.
I would like to try to get a subdomain like ha.mydomain.com to point to my nas server at home, were homeassistant is on and working, but cant seem to get it working, or how to configure this..
So can this be done, and howto do it, or dont use a subdomain or etc etc..

I tried to set up a subdomain and than make a A record: ha, in mydomain.com to point to my nas ip that did not work.
If I make a new site with the subdomain it points to my website at mydomain.com

TIA Appie

 

The last option server (VPS) is in datacenter and NAS is at home behind my router...

 

Yep

 

Yep that's what I was trying to do, but cant get it to work..
I made a DNS A-Record in mydomain.com for the subdomain and pointed that A-Record (subdomain) to the IP from the router, and opened in the router a rule to point subdomain.mydomain.com to the internal NAS IP with its corresponding port (192.168.1.10:1234), with running HomeAssistant (example:subdomain.mydomain.com)
but correct me if I am wrong... to dit it this way

 

did you actually set it to use port 1234 or was that just for an example?
home assistant, by default, uses port 8123

also, no idea what router you have, but is just creating a rule to point the subdomain to the internal nas ip enough?
it might do that for all ports, it might only do it on certain ports. you might need to create a specific port forwarding rule.

 

Yep just as example

I know have some other ports open already to point to my music etc..

But thanks for thinking along...
And TBH this isn't a big deal, as I said I am still just fooling around in HA, and thought this was a quick fix but its not, so for now I am just going to use it local, so I can test and set things up and will try it again when I really need this external acces, maybe just get a new domainname just for HA because they don't cost a lot nowadays,, we will see

Thanks Every one

Appie