To Turn Magento 2 Maintenance Mode ON
bin/magento maintenance:enable
To Turn Magento 2 Maintenance Mode OFF
bin/magento maintenance:disable
If you need to whitelist your IPs
bin/magento maintenance:enable –ip=X1.X1.X1.X1 –ip=X2.X2.X2.X2
To enable maintenance mode for all clients except 192.0.2.10 and 192.0.2.11:
bin/magento maintenance:enable –ip=192.0.2.10 –ip=192.0.2.11