AWS Certified Solutions Architect Associate Test 4

Elastic Load Balancing supports both Internet Protocol version 6 (IPv6) and Internet Protocol version4 (IPv4). Clients can connect to the user's load balancer using either IPv4 or IPv6 (in EC2-Classic) DNS.
However, communication between the load balancer and its back-end instances uses only IPv4.
Theuser can use the Dualstack-prefixed DNS name to enable IPv6 support for communications betweenthe client and the load balancers. Thus, the clients are able to access the load balancer using eitherIPv4 or IPv6 as their individual connectivity needs dictate.
Reference:
http://docs.aws.amazon.com/ElasticLoadBalancing/latest/DeveloperGuide/UserScenariosForEC2.html