Magento2 Maintenance Mode

MaintenanceMode.php

<?php

// 1) Enabled maintenance mode by creating file .maintenance.flag in the var folder
// 2) By pass maintenance mode by creating file .maintenance.ip in the var folder
// 3) IP addresses does not work for ranges only individual ip addresses

if (!preg_match('/^[^\s,]+(,[^\s,]+)*$/', $addresses)) {
            throw new \InvalidArgumentException("One or more IP-addresses is expected (comma-separated)\n");
        }
        
// 4) Comma seperate ip addresses without any spaces 

// ?) Creating a folder called .maintenance.flag will also trigger maintenance mode