SITE MAINTENANCE MAGENTO 2 EXTENSIONS
This extension also called Magento 2 Maintenance mode Extension. Magento 2 Maintenance Extension helps when the live website is under maintenance or maintenance page. Magento 2 Site Maintenance extension is compatible with all browsers. Using this allows you to white list IP addresses. With this extension Magento2 shop either is the front-end of the backend can be accessed from giving IPs.