This read-write value sets how many seconds the primary trunk must stay continuously up before an active backup trunk connection is torn down and traffic reverts to the primary, providing hysteresis in the opposite direction from lportTrkFailureThrsh to avoid rapid flapping between primary and backup. An admin sets this high enough to be confident the primary has genuinely stabilized before tearing down what might be a costly per-minute backup connection. For example, setting lportTrkRestThrsh to 120 ensures the primary trunk must be solidly up for a full 2 minutes before the switch terminates the backup and switches traffic back, avoiding a scenario where a flaky primary causes repeated backup activation and deactivation cycles.