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Sprint cannot currently translate IPV4 addresses (ex. 152.138.17.240) to an actual phone number

Sprint may be able to translate IPV6 addresses (ex. 001:0db8:0000:0042:0000:8a2e:0370:7334) to a phone number.

Interesting, anyone know which aspect of the IPV6 protocol allows for this?

Probably IPv4 is on CGNAT and Sprint doesn't keep the logs of the translation. On IPv6 there's no NAT, and there might be a deterministic relationship between subscription and IP

That, or they don't give devices IPv4 addresses at all and run 464XLAT - according to Wikipedia, quite a few telcos do it that way.

I believe you are correct.

https://news.ycombinator.com/item?id=16440850

464XLAT is a form of CGNAT.

The main difference is whether the subscriber side uses an IPv6 or private IPv4 address, but on the internet side they are equivalent.

Reply on news.ycombinator.com