Yes, you are right.
I can use EC2 instance ID and give them as a node name, then will be able to see in the AppDynamics dashboard.
But my concern is i have three ec2 instance and for ec2 instance id if I have give application-name to all EC2 instance, then in the Appdynamics dashboard in the particular application I can see ec2 instance with the node name, because each node has same name. now if i want to check which node has which ec2 instance id. so from where appdynamics dashboard i can see ec2 instance id.