What Pod Per Node CIDR Range Should You Use for GKE?
Short answer
A /24
Question
Key Takeaways
This question tests your understanding of GKE networking requirements for flexible pod CIDRs, where candidates often overlook the need for additional IPs beyond the pod count for system services and routing.
Configuring GKE pod CIDR ranges requires allocating sufficient IP addresses to support maximum node capacity plus system overhead. Community consensus confirms that a /24 subnet is the correct choice to accommodate up to 100 pods per node.
Common mistake: Many test-takers incorrectly select /25 or /26, assuming only enough IPs for the stated 100 pods, but these subnets do not provide enough usable addresses when accounting for Kubernetes internal networking and overhead.
Expert Analysis
Why the Answer Is Correct
A /24 CIDR block provides 256 total IP addresses, which comfortably exceeds the maximum requirement of 100 pods per node. GKE reserves several addresses within each subnet for cluster control plane communication, node metadata, and internal DNS resolution. Official documentation explicitly states that a /24 is the minimum recommended size to ensure stable pod scheduling and network performance.
Why the Other Options Are Wrong
Subnets like /25 (128 IPs) and /26 (64 IPs) fall short of the required capacity once system overhead is factored in. Option D (/18) allocates far more IPs than necessary, violating best practices for efficient address space management and potentially causing issues with secondary range allocations. Choosing smaller subnets risks pod scheduling failures as the cluster scales.
Community Comment Notes
Users consistently validate option A by referencing GKE’s alias IP and flexible pod CIDR documentation. Commenters highlight that 100 pods require roughly 200+ IPs per node to account for routing and system pods, making /24 the practical minimum. Multiple users share direct links to Google’s official sizing guides, reinforcing the technical accuracy of the answer.
Official Reference
- https://cloud.google.com/kubernetes-engine/docs/how-to/flexible-pod-cidr
- https://cloud.google.com/kubernetes-engine/docs/concepts/alias-ips#cluster_sizing_secondary_range_pods
These links open the official vendor documentation in a new tab.
Exam Strategy
Always add a buffer of 20-30% to your calculated IP needs when selecting CIDR blocks for cloud infrastructure exams. Memorize standard subnet capacities and their corresponding host counts to quickly eliminate insufficient options during timed assessments.
Community Votes
100% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 4 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 4
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PeppaPig 👍 3A 100 pods need 200 ip addresses per node. /24 provides 256 IPs hence answer is A
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[Removed] 👍 2 Answered A/24 is the minimum interval for pods. https://cloud.google.com/kubernetes-engine/docs/concepts/alias-ips?hl=it#cluster_sizing_secondary_range_pods
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jorgesoma 👍 1A is correct! https://cloud.google.com/kubernetes-engine/docs/how-to/flexible-pod-cidr?hl=es-419#cidr_ranges_for_clusters
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Don_Kjeldsen 👍 1 Answered Ahttps://cloud.google.com/kubernetes-engine/docs/how-to/flexible-pod-cidr
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