If you are using Pro or Artist, no internet needed on start up, or when running. That's what the USB Dongle is for. If you are using Elements, that is just a soft-eLicenser and runs off the serial number when first installed.
Although, all change soon with anything Steinberg related. The USB Dongle is being ditched at the front end of next year in favour of a serial number.
https://www.steinberg.net/licensing/