In last post, we have discussed about some basic concepts about the Azure virtual networks. In this post, we will try to further know more about the public and private IPs.
Some of the resources you can associate a public IP address resource with:
- Virtual machine network interfaces
- Internet-facing load balancers
- VPN gateways
- Application gateways
- Azure Firewall
There are two different SKUs available for Public IPs: Basic and Standard. All the public IPs created before introduction of SKUs come under Basic SKU.
Static allocation method means the IP would be assigned when the resource is created and the public IP will be released only when the resource is deleted.
Standard SKUs support only static allocation method. Basic SKU support both static and dynamic allocation. A static public IP is released when the allotment method is changed from static to dynamic.
While creating a public IP resource in Basic SKU, the default allocation method is dynamic. The dynamically set IP address is released when the resource is stopped and restarted.
The Private IP addresses are for allowing communication between the resources within the same Azure virtual network.
Private IP Ranges
Azure assigns private IP addresses to resources from the address range of the virtual network subnet where the resource is. There are three ranges of non-routable IP addresses that are designed for internal networks that won’t be sent over internet routers:
- 10.0.0.0 to 10.255.255.255
- 172.16.0.0 to 172.31.255.255
- 192.168.0.1 to 192.168.255.255
Important point to note is – first four IP addresses from the IP range in a subnet are reserved by Azure and hence cannot be allocated to any other resource. For example, if the subnet’s address range is 10.0.0.0/16, addresses 10.0.0.0-10.0.0.3 and 10.0.255.255 are unavailable.
Private IP addresses can be assigned by both static allocation and dynamic allocation.
In static allocation, you select and assign any unassigned or unreserved IP address in the subnet’s address range.
In dynamic allocation, Azure selects next available IP address from the IP range of the current subnet. This is the default allocation method. The dynamically assigned IP is released if the resource is deleted, or moved to different subnet within same virtual network, or if the allocation method is changed to static and different address was specified.
If the dynamic allocation is changed to static allocation and IP address is not changed, same IP address is used by default. Also when the static allocation is changed to dynamic allocation, the same IP address is assigned as dynamic IP, even if that IP is not available
To assign the network interface to a different subnet, you change the allocation method from static to dynamic. Assign the network interface to a different subnet, then change the allocation method back to static. Assign an IP address from the new subnet’s address range.
I hope you find this information useful. Let me know your thoughts.