I'm not going to let myself be ashamed to admit that I don't know something so here goes.
A situation I've never really encountered here. I've got a domain pointing to my local IP provided by my ISP. The firewall is sending external traffic from the valid ports to a server on the internal network (http, https, apple push services). I have a local OwnCloud VM set to a static IP internally, recognized by the firewall of course, and I want to route external traffic to it.
My question is this. Is there a creative way to redirect a subdomain via an average firewall (SonicWall, nothing fancy) or would I be best to change the apache port on that VM and just force users to use a non-standard port in the URL to access it from the outside? Changing the port seems obvious but I'm wondering if perhaps I'm skipping over a simple way to keep it simple and easy to remember for the end user.