This read-write field enables or disables the automatic trunk-backup feature that activates a designated backup trunk when this primary trunk's link goes down, tying together the various backup-trunk configuration objects, lportTrkFailureThrsh and lportBuTrkRetryInt among them, into an actual armed or disarmed switch. An admin enables this on trunks that have a genuine backup path provisioned and disables it on trunks where no backup exists or where automatic failover is not desired. For example, enabling lportBuTrkOnFailure on a primary trunk with a properly configured backup means a link failure lasting longer than lportTrkFailureThrsh seconds will automatically trigger the backup trunk call setup process rather than requiring manual intervention.