external midi audio playback thru digi 001 interface

how would i monitor audio from an external midi device using a digi 001 interface in sonar 6PE? i hear sound when i switch the 001 interface to monitor mode, but when i switch to regular real time mode i only hear sound from sonar soft synth? is there some kind of signal routing that i need to configure like using pro tools LE or is it some kind of setting in sonar?