Out of curiosity I did some testing with connecting my mobile phone via USB to a routerboard (RB750UP).
I set my phone to share the internet connection over USB and the RouterBoard automatically gave me an LTE interface (lte-1).
When I set-up the LTE interface with NAT I was able to go online over my UMTS connection supplied by my phone.
Only strange thing I noticed is when I disconnect and reconnect my phone. It than gives me LTE-2 interface, and when done again LTE-3 and so on, and so on.
So the question. Why isn’t there 1 static LTE interface since it is only 1 interface at any given time?