Do Cantrips use your character level or class level?

Cantrips seem to be the only type of spell that cares only about your class level.
However, in the multiclassing section they are not mentioned, does this mean that cantrips use your character level, instead of your class level?

Does this mean a Warlock 2 / Fighter 15 can cast an Eldritch Blast with 4 beams just like a level 17 Warlock?