Change DNS Server IP Address in TCA deployed TKG Cluster Nodes

Products

• VMware Telco Cloud Automation

Issue/Introduction

The cluster is deployed with static DNS IP address entered in the TCA cluster deployment workflow.

Environment

vCenter SW Version: 7.x
TCA SW Version: 2.x
TKG SW Version: 1.x

Resolution

Change of static DNS Server IP address , initially set at the time of deployment , through TCA is not supported.

Workaround:

The DNS IP address can be forcefully changed by following below steps.

IMPACT:All nodes will be redeployed, which may lead to potential application downtime depending on the deployment strategy and how high availability is configured for the CNF application.

 

1. List existing vspheremachinetemplate of the cluster.
   kubectl get vspheremachinetemplate -A | grep <cluster-name>

NAMESPACE NAME AGE
xxx-cluster-ccs-1 xxx-cluster-ccs-1 343d
xxx-cluster-ccs-1 xxx-cluster-ccs-1-np1 343d
xxx-cluster-ccs-1 xxx-cluster-ccs-1-np2 343d
   
   
2. Take backup of the all the vspheremachinetemplates of this cluster.
   kubectl get vspheremachinetemplate xxx-cluster-ccs-1 -n xxx-cluster-ccs-1 -o yaml > xxx-cluster-ccs-1-new.yaml
kubectl get vspheremachinetemplate xxx-cluster-ccs-1-np1 -n xxx-cluster-ccs-1 -o yaml > xxx-cluster-ccs-1-np1-new.yaml
kubectl get vspheremachinetemplate xxx-cluster-ccs-1-np2 -n xxx-cluster-ccs-1 -o yaml > xxx-cluster-ccs-1-np2-new.yaml
   
   
3. Edit the new vspheremachinetemplates yaml files and replace nameserver values under network section with correct values. Also change the name field to match with file name.
   network:
devices:
- dhcp4: true
nameservers:
- x.x.x.x
- x.x.x.x


4. Note:Change name field to match with filename (adding "new" to name)
5. Create the new vspheremachinetemplates from those files. Use either create or apply. Both should work.
   kubectl apply -f xxx-cluster-ccs-1-new.yaml
kubectl apply -f xxx-cluster-ccs-1-np1-new.yaml
kubectl apply -f xxx-cluster-ccs-1-np2-new.yaml
   
   
6. There will now be three more vspheremachinetemplates with name new in it.
7. Now edit kcp object to point newly created vspheremachinetemplate in it. After this change new control plane nodes will be rolled out.
   kubectl get kcp -n mdc01-cluster-ccs-1
NAME CLUSTER INITIALIZED API SERVER AVAILABLE REPLICAS READY UPDATED UNAVAILABLE AGE VERSION
xxx-cluster-ccs-1-control-plane xxx-cluster-ccs-1 true true 3 3 3 0 343d v1.23.10+vmware.1

kubectl edit kcp xxx-cluster-ccs-1-control-plane -n xxx-cluster-ccs-1
:
:
machineTemplate:
infrastructureRef:
apiVersion: infrastructure.cluster.x-k8s.io/v1beta1
kind: VSphereMachineTemplate
name: xxx-cluster-ccs-1-new ---> change the name here matching with new template name
namespace: xxx-cluster-ccs-1
   
   
8. Now edit MD object to point newly created vspheremachinetemplate in it. After this change new worker nodes will be rolled out.
   kubectl get md -n xxx-cluster-ccs-1
NAME CLUSTER REPLICAS READY UPDATED UNAVAILABLE PHASE AGE VERSION
xxx-cluster-ccs-1-np1 xxx-cluster-ccs-1 29 29 29 0 Running 343d v1.23.10+vmware.1
xxx-cluster-ccs-1-np2 xxx-cluster-ccs-1 140 140 140 0 Running 343d v1.23.10+vmware.1

kubectl edit md xxx-cluster-ccs-1-np1 -n xxx-cluster-ccs-1
:
:
infrastructureRef:
apiVersion: infrastructure.cluster.x-k8s.io/v1beta1
kind: VSphereMachineTemplate
name: xxx-cluster-ccs-1-np1-new --> new template name


kubectl edit md xxx-cluster-ccs-1-np2 -n xxx-cluster-ccs-1
:
:
infrastructureRef:
apiVersion: infrastructure.cluster.x-k8s.io/v1beta1
kind: VSphereMachineTemplate
name: xxx-cluster-ccs-1-np2-new --> new template name
   
   
9. For a long-term solution, it might be worth considering a design change where DNS can be injected via DHCP, allowing flexibility to change and for easier change management.