A read-write TruthValue controlling whether the IF module uses an external reference clock when true, or its own internal reference clock when false. An external clock reference is typically used to synchronize multiple radios or systems to a common precise timing source, which matters when the deployment needs tight synchronization across units. For example, a site collocating several radios that must stay tightly synchronized to each other might set p2mpClockRefExt to true on each unit to lock them all to one shared external timing reference rather than each drifting independently on its own internal clock.