Hands-free arrival, and uploads that cannot touch Starlink

When the RV comes within about 650 feet of the house, it flips its 5 GHz radio from being an access point to being a client of the home network, and demotes the cellular and satellite links to backup. Leaving flips it back. The two boundaries are deliberately different — roughly 650 feet to arrive, about 1,600 feet to leave — so it cannot sit on the edge flipping back and forth.

Two decisions there are worth spelling out.

The geofence runs on the Cerbo, not in Home Assistant. Routing it through the house would make the thing that switches the network depend on the network already being up. Home Assistant also cannot act at all while the RV is offline, which is precisely when you need this to work.

The dashcam archive is routed so it can only leave over home Wi-Fi. Not "prefers" — only. Its traffic is marked into a routing table with no fallback: if the home gateway disappears, the lookup fails into a blackhole rather than falling through to the default route. The transfer dies instead of quietly finishing over metered satellite. Dashcam footage is exactly the sort of thing that will eat an entire month's plan while nobody is watching.

There is a backstop for the ugly case, too: parked in the driveway with the house access point down, where GPS still insists you are home but the uplink is dead. After a couple of minutes it gives up and reverts to travel mode, so nobody inside is stranded without Wi-Fi.