Azure Standard Public IPs: Embracing Zone Redundancy by Default

As of September 5, 2024, Microsoft Azure Standard Public IP addresses are now zone-redundant by default. This significant enhancement improves the resiliency and availability of your applications and resources in the Azure cloud. This means that when you deploy a Standard Public IP in a region with Availability Zones, it is automatically provisioned across three zones, ensuring your services remain accessible even if a single zone experiences a failure. This automatic redundancy comes at no additional cost and requires no extra configuration steps from your end, simplifying your architecture for high availability.

Key Highlights of Zone-Redundant Azure Standard Public IPs

Automatic Zone Redundancy: Effective September 5, 2024, all newly created Azure Standard Public IPs are zone-redundant by default in regions supporting Availability Zones, without requiring explicit configuration.
Enhanced Resiliency: A zone-redundant IP is distributed across three zones within a region, meaning it can withstand a complete zone outage, significantly improving the availability and robustness of your applications.
Seamless Upgrade Path: If you upgrade an existing Basic SKU Public IP to Standard SKU, it will automatically become zone-redundant, aligning with Microsoft's roadmap to retire Basic SKUs by September 30, 2025.

The Evolution of Azure Public IP Addresses

Azure Public IP addresses are fundamental components that enable your Azure resources to communicate with the internet and public-facing Azure services. They can be dedicated to a resource (static) or assigned temporarily for outbound communication (dynamic). Historically, Azure offered two Stock Keeping Units (SKUs) for Public IPs: Basic and Standard. The introduction of zone redundancy by default for Standard SKUs marks a crucial step in Azure's commitment to building highly available and resilient cloud infrastructure.

Basic vs. Standard SKU Public IPs: A Critical Distinction

Understanding the differences between Basic and Standard SKU Public IPs is essential, especially with the impending retirement of Basic SKUs. Standard Public IPs offer a multitude of advantages that make them the preferred choice for modern cloud deployments.

The table below outlines the key distinctions:

Feature	Basic SKU Public IP	Standard SKU Public IP
Zone Redundancy	Not supported; regional resource.	Zone-redundant by default (in supported regions) or zonal/non-zonal.
Availability Zones	No integration with Availability Zones.	Can be zone-redundant, zonal (tied to a specific zone), or non-zonal.
Security	Open by default; requires Network Security Group (NSG) for inbound control.	Secure by default (closed to inbound flows unless explicitly allowed by NSG).
Allocation Method	Dynamic or Static.	Static only.
Associated Resources	Can be associated with Basic Load Balancer, VMs.	Required for Standard Load Balancer, Azure Firewall, NAT Gateway, VPN Gateway (zone-redundant/zonal).
Retirement Date	Retired on September 30, 2025.	Actively supported and recommended.
Resiliency	Lower resiliency; susceptible to single data center failures.	High resiliency; can survive single zone failures.
Routing Preference	Limited control.	Supported for more granular traffic routing.

As evident from the table, Standard SKU Public IPs are engineered for higher availability and security, aligning with best practices for production workloads. The mandatory upgrade to Standard SKUs before September 30, 2025, underscores their importance in Azure's ecosystem.

Why the Shift to Standard SKUs?

The transition to Standard SKUs is driven by several factors, primarily focusing on enhancing reliability, security, and scalability. Standard IPs provide advanced features like zone-redundancy and stricter security controls, making them a more robust choice for critical applications. The retirement of Basic SKUs signifies Azure's commitment to a more resilient and secure platform.

Zone Redundancy: A Deep Dive into Azure's Resiliency

Zone redundancy is a crucial concept in Azure's architecture, enabling high availability by distributing resources across physically separate data centers within a region, known as Availability Zones. Each Availability Zone is an independent location with its own power, cooling, and networking, designed to be isolated from failures in other zones.

An illustrative diagram showing Azure Availability Zones within a region.

How Zone-Redundant IPs Enhance Application Resiliency

A zone-redundant Public IP address is advertised from all three Availability Zones in a given region. This means that if one zone experiences an outage, traffic can seamlessly be routed through the remaining healthy zones. This inherent capability significantly improves the resilience of applications leveraging these public IPs, ensuring continuous connectivity and minimizing downtime.

Azure Availability Zones for High Availability

Visualizing how applications leverage Availability Zones for high availability and disaster recovery.

For services like Standard Load Balancers, Public IP addresses configured as zone-redundant are vital. They ensure that the load balancer's frontend IP can survive a zone failure, allowing the load balancer to continue distributing traffic to healthy backend resources across the remaining zones.

Configuring Zone Redundancy (or lack thereof)

While Standard Public IPs are now zone-redundant by default, you still have the option to specify a single zone during deployment if your application architecture specifically requires it (creating a 'zonal' IP). However, for maximum resiliency, the default zone-redundant configuration is generally recommended.


resource pip 'Microsoft.Network/publicIPAddresses@2024-01-01' = {
  name: 'myZoneRedundantPublicIP'
  location: resourceGroup().location
  sku: {
    name: 'Standard'
    tier: 'Regional'
  }
  properties: {
    publicIPAddressVersion: 'IPv4'
    publicIPAllocationMethod: 'Static'
    idleTimeoutInMinutes: 4
  }
  zones: [ '1', '2', '3' ] // Explicitly specifying all zones for zone-redundancy
}

The above Bicep code snippet illustrates how you can explicitly configure a Standard SKU Public IP to be zone-redundant by specifying all three zones. However, with the new default behavior, simply creating a Standard SKU Public IP in a region with Availability Zones will achieve zone redundancy without this explicit zones array, unless you choose a specific single zone.

The Practical Implications for Azure Users

The shift to default zone redundancy for Standard Public IPs has several practical implications for Azure users, ranging from new deployments to existing infrastructure management.

New Deployments and Best Practices

For all new deployments, using Standard SKU Public IPs is now the de facto standard and best practice. The implicit zone redundancy simplifies the design of highly available architectures, as you no longer need to explicitly configure this critical aspect for your public-facing endpoints. This streamlines deployment and reduces the potential for misconfigurations that could impact availability.

Moreover, the security-by-default posture of Standard SKUs means that inbound traffic is blocked unless explicitly allowed by a Network Security Group (NSG). This enhances the security of your resources from the outset, requiring a deliberate approach to expose services.

Upgrading Existing Basic SKU Public IPs

Given the retirement of Basic SKU Public IPs by September 30, 2025, upgrading existing Basic IPs to Standard SKUs is a mandatory action. When a Basic SKU Public IP is upgraded to Standard SKU, it automatically gains zone redundancy (in supported regions) without any additional steps. This is a crucial benefit, as it brings existing deployments up to the higher resiliency standard without a complex migration process solely for zone redundancy.

However, it's important to note that direct in-place upgrades that preserve the IP address are not always straightforward, especially if zone redundancy is a requirement. In some scenarios, creating a new Standard SKU Public IP and updating associated resources might be necessary, particularly if the existing Basic IP was not tied to a specific zone and the new architecture demands zone-aware deployment.

The video below provides a practical guide on managing Public IP addresses, including aspects relevant to SKU upgrades and their implications.

An informative video discussing the management of Public and Private IP addresses in Azure, offering insights into their lifecycle and considerations.

Assessing the Impact: A Radar Chart Analysis

To further illustrate the advantages and characteristics of zone-redundant Azure Standard Public IPs, let's consider a radar chart comparing their attributes against Basic SKUs and Zonal Standard SKUs. This chart provides a visual overview of their performance across key dimensions relevant to cloud architecture.

The radar chart illustrates that Zone-Redundant Standard SKU IPs excel in critical areas such as resiliency against zone failures, compatibility with advanced Azure services, and future-proofing your architecture. While Basic SKUs might appear "easier" in terms of initial deployment without explicit security group requirements, their lack of advanced features and impending retirement make them a poor long-term choice. Zonal Standard SKUs offer good security and compatibility but lack the cross-zone resiliency of their zone-redundant counterparts.

Conclusion

The announcement that Azure Standard Public IPs are now zone-redundant by default signifies a major enhancement in Azure's platform capabilities, particularly in the realm of high availability and resiliency. This change simplifies the design and deployment of robust applications, ensuring that public-facing endpoints can withstand single zone failures without manual intervention. As the retirement date for Basic SKU Public IPs approaches, the transition to Standard SKUs becomes not just a recommendation but a necessity, bringing with it the inherent benefits of enhanced security, advanced feature compatibility, and now, automatic zone redundancy. Embracing these modern public IP configurations is crucial for building future-proof and resilient cloud solutions on Azure.