Despite I tested a lot of LTE-Modems for ModemManager and NetworkManager. I never knew what did happen behind it.
#ipv6
here Aleksander Morgado explains it
modemmanager.org/docs/modemman…
IP connectivity setup in LTE modems
An outline of the different IP settings a ModemManager bearer object may expose, and the expected actions the host would require to perform to set up the IP addressing in the modem.modemmanager.org