port forwarding stopped working
Our router is set up to provide addresses on the local network using DHCP, in a range starting at 10.1.10.150. We have some servers on the local network that have fixed IP addresses *below* that range. We set up port forwarding (using non-common port numbers) to provide external access to those servers.
This has worked flawlessly for some years now. A few days ago, it stopped working. Port testing tools would show the port(s) in question to be closed.
We contacted Comcast and a support technician had us lower the DHCP range (down to 10.1.10.2) to include the servers, even though they have fixed IP addresses, and that seems to work. We confirmed it yesterday by setting it back to 10.1.10.150 (broken), and 10.1.10.2 (fixed).
Why is this suddenly necessary? No one in our organization changed the router in any way. And also, the documentation (https://business.comcast.com/help-and-support/internet/comcast-business-ip-gateway-static-firewall/) says:
"If the IP address of the local server PC is assigned by DHCP, it may change when the PC is restarted. To avoid this, you can assign a static, private IP address to your server by manually configuring the server’s IP settings. Be sure that the assigned IP is outside the range of DHCP addresses set on the Comcast Gateway but in the same subnet as the rest of your LAN".
I'm nervous to leave it this way, it seems like if we add a server and forget to give it a fixed address, might it get one vis DHCP that collides with one of the existing servers?