Reserve public IP addresses and use them as virtual IP (VIP) addresses for your applications. Use IP reservation for VIPs when your applications need static public IP addresses, or if you need to update your applications by swapping the reserved IP addresses. You can reserve up to 5 addresses per subscription at no additional cost and assign them to the Azure Cloud Service of your choice. You can also reserve another 5 (for a total of 10) addresses at additional cost.
Learn more about Reserved IPs