> The first step should've been looking up the hostnames to see what you're dealing with.

Great point.

After looking up 29 of the IP addresses, it seems 28 of them (including all the overlapping IP addresses) are T-Mobile.

Among the 29 I checked, there is 1 IP address with a different hostname (Verizon). This address is unique and not shared with any other users.

Presumably all these forum members based in New York City are all also T-Mobile customers there, it seems?

> It could be several things, but it's most likely either CGNAT, or you're using a CDN and these are their ranges.

We do, but it's configured to pass the user's origin IP to our site, rather than the CDN's IPs.