The service Deny IPv6 is part of the Default Policy Domain that ships with the product.
This is just one method of adding services to a role. There are other methods that you can review by clicking on Help in the Policy Manager application.
Policy to block certain protocols such as IPv6 can also be accomplished via CLI. A description is available at this link: "
KCS 1111:, "How to configure policy to drop or block IPV6 packets on Securestacks and Modular switches/routers