"Where do you know that route from?"
Translation:Dari mana kamu tahu tentang rute itu?
What does "tentang" do in this sentence and would it have the same meaning if it wasn't there?
'Tentang' means about. I think it would still have the same meaning without it.
Although, the Indonesian translation here, "Dari mana kamu tahu tentang rute itu?" is more appropriate if the English sentence is "Where do you know about that route?"