The three IPv6 features supported in an NSX-T Data Center design are IPv6 static routing, IPv6 Distributed Firewall, and IPv6 VXLAN. IPv6 static routing is a fundamental routing method supported by NSX-T. The IPv6 Distributed Firewall feature allows the implementation of security policies for IPv6 traffic. Lastly, while traditional VXLAN does not inherently support IPv6, NSX-T has incorporated support for IPv6 VXLAN. IPv6 OSPF is not a typical feature in NSX-T designs, IPv6 switch security is a vague term that doesn't specify a clear feature, and IPv6 DNS is generally handled outside the scope of NSX-T designs.