464xlat is standardized and can be set up automatically. All it needs is a DNS query to any v4-only hostname to detect if DNS64 is in operation. Most 4g modems

464xlat is standardized and can be set up automatically. All it needs is a DNS query to any v4-only hostname to detect if DNS64 is in operation. Most 4g modems work as routers exposing an ethernet interface to the host, so it's certainly possible that it's doing 464xlat in the firmware, and if it doesn't tell you on some sort of status page then the only real hint that it's doing it would be a reduced path MTU. I wouldn't be surprised if T-Mobile offer legacy service to any type of business contract or non-phone client though.