BYO Subnet

[Bryce-Soghigian]

Add support to karpenter for BYO Subnet per AKSNodeclass

A workload may require splitting cluster nodes into separate pools for logical isolation. Separate subnets dedicated to each node pool in the cluster can help support this isolation, which can address requirements such as having noncontiguous virtual network address space to split across node pools.

The goal of this issue is to define how unique subnets in a custom vnet will work inside of karpenter. It will be largely based on the existing AKS Nodepool VNETSubnetID field.

Acceptance Criteria

• BYO Subnet per AKSNodeclass
• supported for both Node Auto Provisioning and Self Hosted Karpenter
• we will not be supporting --pod-subnet-id as karpenter currently only supports azure cni + overlay

Limitations

• If you expand your VNET after creating the cluster, you must update your cluster before adding a subnet outside the original CIDR block.
• System pods must have access to all nodes and pods in the cluster to provide critical functionality, such as DNS resolution and tunneling kubectl logs/exec/port-forward proxy.
• Internal load balancers default to one of the node pool subnets.
• All Subnets assigned to nodepools must belong to the same virtual network

---

• Please vote on this issue by adding a 👍 reaction to the original issue to help the community and maintainers prioritize this request
• Please do not leave "+1" or "me too" comments, they generate extra noise for issue followers and do not help prioritize the request
• If you are interested in working on this issue or have submitted a pull request, please leave a comment