This read-write value sets how many backup-trunk call setup attempts the switch makes within a single retry cycle before giving up on that cycle, with lportBuTrkCycleInt governing how long to wait before starting a whole new cycle. An admin sets this to bound how persistently the switch tries to establish backup connectivity on each attempt series, balancing thoroughness against not endlessly hammering a call-setup path that clearly is not succeeding. For example, with lportBuTrkRetryNum set to 3, the switch will make three attempts spaced by lportBuTrkRetryInt seconds before pausing until the next full retry cycle begins.