Provide a Flat Network Scaling Solution to AKS - Azure CNI Pod Subnet - Static Block Allocation

Microsoft

Jul 24, 2025

We are excited to announce the general availability of Azure CNI Pod Subnet - Static Block Allocation – a networking solution that transforms how you scale Azure Kubernetes Service (AKS) clusters! This long-awaited feature is now here, providing enterprise-grade flat networking for clusters in unprecedented capacity.

What is Azure CNI Pod Subnet - Static Block Allocation?

Azure CNI Pod Subnet - Static Block Allocation revolutionizes AKS networking by expanding cluster capacity from 65K to 1M pods – a game-changing 15x increase that eliminates traditional scaling barriers.

Instead of assigning a batch of random individual IP addresses to each node, this innovative approach assigns dedicated Azure subnet CIDR ranges directly to nodes. Every pod scheduled on a node receives its IP address from that node's pre-allocated CIDR block, raising IP limit and simplifying massive deployments.

The result is you gain unmatched flexibility with separate node and pod subnets, granular control over NAT and NSG policies, isolated workloads at the pod level, and VNet-native pod networking that maintains peak performance. It also seamlessly works with Azure CNI Powered by Cilium to provide advanced networking capabilities and comprehensive network policy enforcement.

Why is Azure CNI Pod Subnet - Static Block Allocation needed?

Kubernetes network solutions are challenging to plan due to rapidly evolving business needs. AKS users often face difficulties balancing simplicity, security, and scalability, while environmental changes further increase management costs.

Many AKS users need a flat network architecture, pods with direct inbound connectivity, and Azure-native solution integrations, but traditional flat networks couldn't scale beyond 65K pods. Until the launch of static block, customers either choose overlay networks to achieve massive scale or sacrifice the benefits of flat networking.

 Azure CNI Pod Subnet - Static Block Allocation enables VNet-routed IP addresses that can scale to over 1M pods, providing the simplicity and low latency of a flat network. Each node receives pre-allocated CIDR blocks, and all pods on that node obtain IP addresses from these ranges. This approach delivers massive scale, previously only available with overlay networks (up to 1M pods) while maintaining all the benefits of a flat network architecture. It also works seamlessly alongside Azure CNI Pod Subnet - Dynamic IP Allocation, simply deploy it on new node pools with dedicated subnets.

AKS users can scale up AKS network solutions with minimal effort while maintaining enterprise-grade reliability and security.

Key Benefits That Matter to You

Massive Scale Increase: Break through the 65K pod limitation and scale up to 1M pods per cluster. This isn't just a number—it's about giving you the freedom to build and scale without hitting unexpected networking limits.

High Performance: AKS users’ pods get routed on the VNet which is a benefit for ingress/egress, eliminating unnecessary network hops and reducing latency for VNet-native pod networking.

Efficient IP Management: AKS users now can allocate CIDR blocks to nodes. This approach raises the IP scalability limit for large-scale deployments.

Unmatched Flexibility:

- Work seamlessly with existing clusters with Azure CNI Pod Subnet - Dynamic IP Allocation

- Share pod subnets across multiple node pools or even different clusters.

- Scale your node and pod networks independently

Granular Control and Security: Since pods get their own dedicated subnet, AKS users can:
- Apply different network security policies to pods vs. nodes.