Port forwarding

[stevech]

Received Grandstream ATA today.
For QoS reasons, I put it ahead of my home router. That is, the WAN port of the Grandstream connects to my cable modem.

Working fine, except, of course, port 80 on my home router is no longer visible to the Internet. So my domain name port 80 yields the Grandstream's web page.

Must I change my home web server to use other than port 80? I assume the Grandstream will port-forward all but those it wants to use, such as 80 and those used by ATA VoIP functions and admins.

I "assume" the Grandstream will port-forward - but when I moved my web server to port 81 and changed port forwarding on my home router to match, no workie.

Any way for the Grandstream to NOT use port 80 and forward it to my home router?

I don't want to put the Grandstream on a LAN port of my home router for fear that if I have QoS issues, my home system would be faulted.