I have certain doubts about load balancing VMs in Azure.
When i add a vm to an existing deployment(already running VM) it assigns the same dns name to the added VM but there is no Virtual IP assigned to the VM. But the port shows load balanced VM.
I believe what you're saying is that VM number 2 through N appear to come online with the same DNS name as VM number 1.
This is expected behavior. The VIP is the Virtual IP address, which is the DNS name on the outside edge of the load balancer. This should be the same for every load balanced machine behind the load balancer. The internal IP of each instance is known as the DIP, or Dedicated IP address.
The job of the load balancer is to take requests against the VIP and redistribute those calls to each of the DIPs. Once the request is serviced by an individual instance, it is routed back to the caller via the load balancer.
Is that what you're seeing, or am I misunderstanding your question?