Public IP addresses

Public IP addresses allow Internet resources to communicate inbound to Azure resources. Public IP addresses enable Azure resources to communicate to Internet and public-facing Azure services. You dedicate the address to the resource until you unassign it. A resource without an assigned public IP can still communicate outbound. Azure automatically assigns an available dynamic IP address for outbound communication. This address isn't dedicated to the resource and can change over time. For more information about outbound connections in Azure, see Understand outbound connections.

In Azure Resource Manager, a public IP address is a resource that has its own properties.

The following resources can be associated with a public IP address:

• Virtual machine network interfaces
• Virtual Machine Scale Sets
• Azure Load Balancers (public)
• Virtual Network Gateways (VPN/ER)
• NAT gateways
• Application Gateways
• Azure Firewalls
• Bastion Hosts
• Route Servers
• Api Management

For Virtual Machine Scale Sets, use Public IP Prefixes.

At-a-glance

The following table shows the property a public IP can be associated to a resource and the allocation methods. Public IPv6 support isn't available for all resource types at this time.

Top-level resource	IP Address association	Dynamic IPv4	Static IPv4	Dynamic IPv6	Static IPv6
Virtual machine	Network interface	Yes	Yes	Yes	Yes
Public Load balancer	Front-end configuration	Yes	Yes	Yes	Yes
Virtual Network gateway (VPN)	Gateway IP configuration	Yes (non-AZ only)	Yes	No	No
Virtual Network gateway (ER)	Gateway IP configuration	Yes	Yes	Yes (preview)	No
NAT gateway	Gateway IP configuration	No	Yes	No	No
Application Gateway	Front-end configuration	Yes (V1 only)	Yes (V2 only)	No	No
Azure Firewall	Front-end configuration	No	Yes	No	No
Bastion Host	Public IP configuration	No	Yes	No	No
Route Server	Front-end configuration	No	Yes	No	No
Api Management	Front-end configuration	No	Yes	No	No

IP address version

Public IP addresses can be created with an IPv4 or IPv6 address. You may be given the option to create a dual-stack deployment with a IPv4 and IPv6 address.

SKU

Public IP addresses are created with a SKU of Standard or Basic. The SKU determines their functionality including allocation method, feature support, and resources they can be associated with.

Full details are listed in the table below:

Public IP address	Standard	Basic
Allocation method	Static	For IPv4: Dynamic or Static; For IPv6: Dynamic.
Idle Timeout	Have an adjustable inbound originated flow idle timeout of 4-30 minutes, with a default of 4 minutes, and fixed outbound originated flow idle timeout of 4 minutes.	Have an adjustable inbound originated flow idle timeout of 4-30 minutes, with a default of 4 minutes, and fixed outbound originated flow idle timeout of 4 minutes.
Security	Secure by default model and be closed to inbound traffic when used as a frontend. Allow traffic with network security group (NSG) is required (for example, on the NIC of a virtual machine with a Standard SKU Public IP attached).	Open by default. Network security groups are recommended but optional for restricting inbound or outbound traffic.
Availability zones	Supported. Standard IPs can be non-zonal, zonal, or zone-redundant. Zone redundant IPs can only be created in regions where 3 availability zones are live. IPs created before zones are live won't be zone redundant.	Not supported.

Virtual machines attached to a backend pool do not need a public IP address to be attached to a public load balancer. But if they do, matching SKUs are required for load balancer and public IP resources. You can't have a mixture of basic SKU resources and standard SKU resources. You can't attach standalone virtual machines, virtual machines in an availability set resource, or a virtual machine scale set resources to both SKUs simultaneously. New designs should consider using Standard SKU resources. For more information about a standard load balancer, see Standard Load Balancer.

IP address assignment

Public IPs have two types of assignments:

• Dynamic - The IP address isn't given to the resource at the time of creation when selecting dynamic. The IP is assigned when you associate the public IP address with a resource. The IP address is released when you stop, or delete the resource. Dynamic public IP addresses are commonly used for when there's no dependency on the IP address. For example, a public IP resource is released from a VM upon stop and then start. Any associated IP address is released if the allocation method is dynamic. If you don't want the IP address to change, set the allocation method to static to ensure the IP address remains the same.

• Static - The resource is assigned an IP address at the time it's created. The IP address is released when the resource is deleted. When you set the allocation method to static, you cannot specify the actual IP address assigned to the public IP address resource. Azure assigns the IP address from a pool of available IP addresses in the Azure location the resource is created in.

Static public IP addresses are commonly used in the following scenarios:

• When you must update firewall rules to communicate with your Azure resources.
• DNS name resolution, where a change in IP address would require updating A records.
• Your Azure resources communicate with other apps or services that use an IP address-based security model.
• You use TLS/SSL certificates linked to an IP address.

Resource	Static	Dynamic
Standard public IPv4	✅	x
Standard public IPv6	✅	x
Basic public IPv4	✅	✅
Basic public IPv6	x	✅

Domain Name Label

Select this option to specify a DNS label for a public IP resource. This functionality works for both IPv4 addresses (32-bit A records) and IPv6 addresses (128-bit AAAA records). This selection creates a mapping for domainnamelabel.location.chinacloudapp.cn to the public IP in the Azure-managed DNS.

For instance, creation of a public IP with the following settings:

• contoso as a domainnamelabel

• China North 3 Azure location

The fully qualified domain name (FQDN) contoso.chinanorth3.cloudapp.chinacloudapi.cn resolves to the public IP address of the resource.

If a custom domain is desired for services that use a public IP, you can use Azure DNS or an external DNS provider for your DNS Record.

Domain Name Label Scope (preview)

Public IPs also have an optional parameter for Domain Name Label Scope, which defines what domain label an object with the same name will use. This feature can help to prevent "dangling DNS names" which can be reused by malicious actors. When this option is chosen, the public IP address' DNS name will have an additional string in between the domainnamelabel and location fields, e.g. contoso.fjdng2acavhkevd8.westus.cloudapp.Azure.com. (This string is a hash generated from input specific to your subscription, resource group, domain name label, and other properties).

The domain name label scope can only be specified at the creation of a public IP address.

The value of the Domain Name Label Scope must match one of the options below:

Value	Behavior
TenantReuse	Object with the same name in the same tenant will receive the same Domain Label
SubscriptionReuse	Object with the same name in the same subscription will receive the same Domain Label
ResourceGroupReuse	Object with the same name in the same Resource Group will receive the same Domain Label
NoReuse	Object with the same name will receive a new Domain Label for each new instance

For example, if SubscriptionReuse is selected as the option, and a customer who has the example domain name label contoso.fjdng2acavhkevd8.chinanorth3.cloudapp.chinacloudapi.cn deletes and re-deploys a public IP address using the same template as before, the domain name label will remain the same. If the customer deploys a public IP address using this same template under a different subscription, the domain name label would change (e.g. *contoso.c9ghbqhhbxevhzg9.chinanorth3.cloudapp.chinacloudapi.cn).

Other public IP address features

There are other attributes that can be used for a public IP address (Standard SKU only).

• The Global Tier option creates a global anycast IP that can be used with cross-region load balancers.

• The Internet Routing Preference option minimizes the time that traffic spends on the Microsoft network, lowering the egress data transfer cost.

Limits

The limits for IP addressing are listed in the full set of limits for networking in Azure. The limits are per region and per subscription.

Contact support to increase above the default limits based on your business needs.

Pricing

Public IPv4 addresses have a nominal charge; Public IPv6 addresses have no charge.

To learn more about IP address pricing in Azure, review the IP address pricing page.

Limitations for IPv6

• VPN gateways can't be used in a virtual network with IPv6 enabled, either directly or peered with "UseRemoteGateway".

• Azure doesn't support IPv6 communication for containers.

• Use of IPv6-only virtual machines or virtual machines scale sets aren't supported. Each NIC must include at least one IPv4 IP configuration (dual-stack).

• IPv6 ranges can't be added to a virtual network with existing resource navigation links when adding IPv6 to existing IPv4 deployments.

• Forward DNS for IPv6 is supported for Azure public DNS. Reverse DNS isn't supported.

• Routing Preference Internet isn't supported.

For more information on IPv6 in Azure, see here.

Next steps

• Learn about Private IP Addresses in Azure

• Deploy a VM with a static public IP using the Azure portal