Thanks for the ideas. I just tried 111111, 222222,333333, 444444, 555555, 666666, 777777, 888888, 999999,000000 as well as the the same but 5 in length.
Dahua config tool doesn't seem to see it. Hikvision SADP tool doesn't see it. ONVIF Device Manager can see it but says unauthorized access...