public function findFailedLAGPorts() {
        // find all configured LAG ports
        $lagPorts = $this->isAggregatePorts();

        // find all attached ports
        $attachedPorts = $this->portAttachedIds();

        foreach ($lagPorts as $portId => $isLAG) {
            if (!$isLAG) {
                unset($lagPorts[$portId]);
                continue;
            }

            if ($attachedPorts[$portId] != 0)
                unset($lagPorts[$portId]);
        }

        // we should be left with configured but unattached LAG ports
        return( $lagPorts );
    }