1: Login to NetXGATE NG Dashboard as an administrator with read and write permission .
2: Go to Configuration , > Network Settings > Select the WAN port on which you want to add Additional IP Addresses (IP Alias ) . .
3: Under WAN Static Mode go to Additional IP Addresses (IP Alias ) option and Enable it .
4: Under IP Alias List - Enter a IPs provided by your ISP. ( e.g. - 111.100.101.51/255.255.255.255 ).
After making the above necessary configuration, Click Save and Restart Service.