Hello @juancom
It sounds like you're trying to get a port mapping through two layers of NAT firewalls (an outer router+firewall that your Nest WiFi Router is connected to, and the Nest WiFi Router itself). To do that, you'll need to create a port mapping in the outer router that points to the WAN IP address of your Nest WiFi Router. To find that, open the Google Home app, then "Wifi", then tap the "3 points" at the top (yours might be a different number than 3), then tap on your router name under "Nest Wifi router", and finally tap the gear icon in the upper right corner. That will open a screen with some detailed information about your Nest WiFi Router. Mid-way down that screen, under "Wi-Fi Information" you should see "WAN IP: ..." with your Nest WiFi Router's WAN IP address, which should be getting assigned by your outer router. That's the address you want to use when setting up the port mapping in the outer router.
You'll then need to set up a similar port mapping in the Nest WiFi Router to the client machine inside your Nest WiFi network as well. This page should help with that: https://support.google.com/googlenest/answer/6274503?hl=en
