IP Addresses

- Public IP(from internet) vs Private IP(inside network)

- Public IP used for Virtual Machines, Load Balancers, VPN Gateways, Application Gateways 

- Private IP used for Virtual Machines, Load Balancers, Application Gateways 

https://docs.microsoft.com/en-us/azure/virtual-network/virtual-network-ip-addresses-overview-arm

Other types of IP Addresses, available in both Public or Private IP Addresses.They are Dynamic IP and Static IP(ARM)

Dynamic, generated from pool of IP addresses.

Static, can't be set manually but we can fix it to a machine once generated.

Can setup or point custom domain names(DNS) to the Azure domain using a CNAME record.

Static may be required for security reasons; firewall settings.

Let's say a webservice externally setup but need to setup firewall settings to allow our azure app to access the web service.

To set the A record of a DNS

IP based scurity model.

For SSL certificate.

LIMITs:

4096 private IPs per VNET.

60 public dynamic IPs.

20 public static IPs.

Static IPs have a cost: first 5 free, rest cost $0.004/hr

https://azure.microsoft.com/en-us/pricing/details/ip-addresses/