Use the EC2Snitch for simple cluster deployments on Amazon EC2 where all nodes in the cluster are within a single region. The region is treated as the data center and the availability zones are treated as racks within the data center. For example, if a node is in us-east-1a, us-east is the data center name and 1a is the rack location. Because private IPs are used, this snitch does not work across multiple regions.
When defining your keyspace strategy options, use the EC2 region name (for example,``us-east``) as your data center name.