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Difficulty: MediumConfigure Azure Kubernetes Service (AKS)

Your company is deploying a new Azure Kubernetes Service (AKS) cluster named aks-billing to host a financial application. You must configure the cluster to use the Azure CNI network model where nodes and pods share the same subnet.

The deployment configuration has the following parameters:
* Initial node count: 4
* Maximum pods per node: 20

Excluding the standard five IP addresses reserved by Azure, what is the minimum number of IP addresses that must be available in the subnet to support the cluster nodes, pods, and rolling upgrades?

  1. A
    84
  2. B
    85
  3. 105Answer
  4. D
    5

Answer

105
The correct calculation for the minimum IP addresses required by an Azure CNI cluster in a single subnet is based on the formula (N+1)+((N+1)×M)(N + 1) + ((N + 1) \times M), where NN is the number of nodes and MM is the maximum number of pods per node. For 4 nodes and 20 pods per node, this equals (4+1)+((4+1)×20)=5+100=105(4 + 1) + ((4 + 1) \times 20) = 5 + 100 = 105. This ensures that the subnet has sufficient IP addresses for the initial nodes, their pods, and an additional surge node with its pods during rolling upgrades.

Step-by-Step Solution

1
Identify the network model and the formula for Azure CNI IP planning.
The network model is Azure CNI. The formula to calculate required IP addresses is (N+1)+((N+1)×M)(N + 1) + ((N + 1) \times M), where NN represents the initial number of nodes, and MM represents the maximum number of pods per node.
Azure CNI pre-allocates IP addresses for all pods on every node, including an additional node (surge node) created during upgrades.
2
Substitute the given values into the formula: N=4N = 4 nodes and M=20M = 20 pods per node.
Calculation: (4+1)+((4+1)×20)=5+(5×20)=5+100=105(4 + 1) + ((4 + 1) \times 20) = 5 + (5 \times 20) = 5 + 100 = 105.
This computes the sum of the total nodes (including the upgrade node) and the total pre-allocated pod IP addresses for those nodes.
3
Verify if the question excludes Azure reserved IPs and determine the final minimum requirement.
The question specifically asks for the requirement excluding the five standard reserved IPs, so the final count is 105.
Azure reserves 5 IP addresses per subnet, which would increase the required subnet size but are not part of the active cluster IP footprint calculated here.

Key Concept

IP address planning for Azure Kubernetes Service (AKS) using the Azure CNI network model
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Topics

Configure Azure Kubernetes Service (AKS)

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