> IP and geo location can work up to the state (country), that's it... and that doesn't include the roaming.
IP location can work at the postal code level, if the ISP's assignment scheme is granular enough and they are either publishing a corresponding geofeed or somebody is just reverse engineering one based on data collection.
The latter works very similarly to Wi-Fi geo positioning: Devices that have a GPS position source report the observed location of a given IP address; devices without one make use of it.
> So just forget IP and geolocation.
Yes, for the <1% of people actively doing something against it (e.g. using VPNs), for some other edge cases, and importantly for mobile data roaming. Otherwise, it's surprisingly accurate these days.
How does that follow? The more densely populated an area is, the more accurate geo-IP usually is as well, just like with other infrastructure (postal code areas are smaller in cities etc.)
Regarding NAT, CG-NATs are usually still reasonably close to the first interconnection point to keep latency low. And as that stops being the case, IPv6 is getting more and more common in any case, precisely because CG-NAT doesn’t scale that well.
IP location can work at the postal code level, if the ISP's assignment scheme is granular enough and they are either publishing a corresponding geofeed or somebody is just reverse engineering one based on data collection.
The latter works very similarly to Wi-Fi geo positioning: Devices that have a GPS position source report the observed location of a given IP address; devices without one make use of it.
> So just forget IP and geolocation.
Yes, for the <1% of people actively doing something against it (e.g. using VPNs), for some other edge cases, and importantly for mobile data roaming. Otherwise, it's surprisingly accurate these days.