How to read router measurements (upnp) from different subnet?


I used to have a cable modem next to my home assistant installation in the same subnet but now I had to move all the IOT stuff behind another wireless router along with home assistant installation. At the same time, I lost all the cable modem measurements (via upnp).

I checked that I’m able to reach cable modem upnp port from the laptop in which I have installed home assistant as a container. I did that checking by using Nmap and I wonder should home assistant discover that old modem somehow or should I do some manual stuff over there? The only difference is that now home assistant and old router are in the different subnets but the upnp port is still reachable (routed) between them.

Upnp discovery works somehow since my home assistant installation is able to read the new router measurements. The new router is connected to old one and I just move all the IOT stuff behind it.

Any ideas what I could try to do? And thanks in advance:-)