AKS cluster is in Failed state. How can I revert the changes

Hi @Urmila Purohit

AKS (Azure Kubernetes Service) does not support changing or replacing the virtual network (VNet) or subnet of a cluster after it has been created. If you attempt to modify the VNet settings post-deployment, it can break the connection between the control plane and the cluster nodes, leading to mismatched network configurations. This disruption causes operations like cluster updates and node pool management to fail, even though the underlying virtual machines (VMSS instances) may still be healthy enough to continue running workloads.

Because reverting a VNet change on an existing cluster is unsupported and will not reliably restore cluster health, the recommended path is:

1. Verify Cluster and Node Pool State  
   Azure Portal: Navigate to **Kubernetes services > [YourCluster] and check the Overview and Node pools blades.  
   Azure CLI:
   az aks show --resource-group MyRG --name MyAKSCluster --query provisioningState
   az aks nodepool list --resource-group MyRG --cluster-name MyAKSCluster
2. Create a New AKS Cluster in the Correct VNet  
   Ensure you have a subnet delegated to Microsoft.ContainerService/workload and NSGs/UDRs that allow outbound HTTPS to required Azure endpoints (e.g., mcr.microsoft.com:443).
3. Migrate Your Workloads  
   Export Kubernetes manifests, Helm charts, or use backup/restore tools such as Velero.   Deploy or restore your workloads into the new cluster.

4.Validate Application Functionality  
Test connectivity, service endpoints, and app functionality in the new cluster.  
Confirm pods, services, and ingress (if used) are operating as expected.

Once everything is confirmed to be working as expected, you should decommission the old, failed cluster to avoid unnecessary resource consumption.

 Please refer : Concepts - CNI networking in AKS - Azure Kubernetes Service | Microsoft Learn

                      Azure Kubernetes Service cluster/node is in a failed state - Azure | Microsoft Learn