GPIO 20 war’s!
TPLink CPE210/CPE510 switch off POE pt (pass through) on LAN1
(OpenWRT)
echo 20 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio20/direction
echo 1 > /sys/class/gpio/gpio20/value # ON
Turn on passive POE LAN0 to LAN1:
echo 20 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio20/direction
echo 0 > /sys/class/gpio/gpio20/value # OFF
(just for google…) 
(Beweisphoto <g>)