i was happy too early 
modem is up, registered, IPv4 DHCP -> OK
but ...
after modem getting IP, nothing is forwarded to LTE interface
only traffic is exactly 666 byte, when LTE get DHCP response, and that is it
tried with two SIM card, different operators
same, dhcp OK and then nothing else work
tried reseting with "AT&F" "AT&W" "ATZ" ...
still nothing