QuoteBut IPv6 is far from being universally used. So, Vista will also support the current IPv4. The side effect, according to Mockapetris, is that a Vista PC will make two DNS requests, one for each IP version, instead of just one. "It is going to try a DNS lookup for the IPv6 address and then a DNS lookup for the IPv4 address," Mockapetris said. "It just uses more DNS, and until we increase the supply, things are going to go slower."