VM/Host affinity rules are not working as expected on vCenter

Products

• VMware vCenter Server

Issue/Introduction

• A group of VMs configured with a VM/Host rule set to "Keep Vms together" are NOT running on the same host as they are supposed to.
  
  
• When validated, the VMs configured in the above group are running on two different hosts which doesn't satisfy the Rule 

Environment

• VMware vCenter Server 7.x
• VMware vCenter Server 8.x

Cause

• DRS is not  set to fully automated
• Even Distribution of VMs is not enforced to "MUST" in DRS settings

Resolution

1. Ensure DRS is set to fully automated mode 
2. Also,Go to DRS Settings → set rule enforcement level to “Must” 
   
   
   
   
3. Now, all the VM's configured with VM/Host Rules  to "Set VMs together" will stay on the same host (It can be any host in the cluster)