network addressing scheme changed, can't find processor on network

The processor was set up with the static ip address of 192.168.10.75, subnet of 255.255.255.0, with the gateway of 192.168.10.1. The AV guy had integrated a remote control for the AV that would also control the lights. All was working great.

Today I went to add a couple of scenes but when I went to upload the programming, noticed it wasn't communicating with the processor. I did an ipconfig and saw that network was changed completely to 192.168.50.x and when I ran a network scanner, the Lutron processor was not showing up at all presumably because its IP address is a host for a different network.

Here is the weird part: The remote control is still working. Is it possible that the remote control is somehow able to connect to 192.168.10.75 from 192.168.5.x? Normally, I'd call the AV guy and see what he did, but there was some sort of drama and he may not be available but I can't find the processor on the network and if I connect directly and change it, then for sure the integration link would be broken. So I guess my biggest question is it possible for the remote control to communicate with the QS processor even though they are on different addressing schemes? Can the switch just pass along the traffic without going through the router? I'm trying to figure out whether the AV guy used some networking trick to make sure his remote could reach the processor on purpose or this is just an accident. I'm kind of in a weird position here because the remote is technically working (somehow) but I can't make any changes. I hope the AV guy comes back.

Yes this can be done on the network side, allowing you to pass traffic between VLANs. But the remote control may not be WiFi- it could be RF talking to its controller (not sure what equipment you have there). This is one of the main reasons when I setup our systems I use a DHCP reservation in the router instead of statically addressing for our equipment- that way id the address scheme changes you aren't stuck with an unconnectable device like your QS processor. Sure its a tiny bit more work for the network guy but its the proper way to do it.

You can do this even without VLANs. Some of the cameras we sell come with static IP addresses (ex:192.168.1.200). If I connect that camera to a 192.168.50.x network and change my computer IP address to 192.168.1.x I can communicate with the camera but not with anything with a 192.168.50.x address.

As long as the AV system is sending directly to 192.168.10.75 it will work. If the HQS processor is set to DHCP and it reboots, it will get a 50.x address and the link will be broken. If you manually change the HQS address to anything other than 10.75 the link will break.

Well fortunately the change I was going to make was minor and the rest of the system is functioning correctly. I hope by the time I need to access the system for something more substantial, the "drama" is gone and he's back but there is a possibility that may not happen.

In the meantime, could I get one of my old walking around routers and set it up to match what the house used to be before the change and connect that to the system to make my changes and then plug the house ethernet back in? That way the networking in the processor is intact so if the AV guy did some fancy routing (VLANs, subnets, or whatever) they'll stay in place, or if the remote is just directly communicating by shear luck, that would also stay in place? I just want to have a game plan in case I really need to access the system.

If you're sure the Lutron processor has the expected IP address, then that's a great idea. Or you could always just change the IP address settings of your laptops ethernet port to the same IP range and plug into the processor and upload that way.

Have you tried checking out the subnet mask and CIDR notation for your new network? These might help you locate your Lutron processor and avoid breaking the integration link. As for your remote control, it's possible that it's still able to connect to your processor despite the different addressing schemes. It's also possible that the AV guy used some networking trick to make it work, but without his help, it might be tough to figure it out. In the meantime, you can check out this link for more info on subnet masks and CIDR notation: https://routeripnet.com/what-is-netmask-subnet-cidr/.