"We are not aware of anybody else doing" a free recursive DNS service that supports IPv6, Ulevitch says. "There's no financial angle; we just want to encourage people to use an IPv6 DNS service."

Until now, network engineers experimenting with IPv6 had to encapsulate their traffic to transverse IPv4-based DNS servers.

"People want to experiment with IPv6, and we have DNS set up to support them," Ulevitch says. "We are trying to help push traffic and resources over to IPv6. If you actually want to reach IPv6-only resources, you need to use DNS resources that you can talk to over IPv6."

The IPv6 addresses for the OpenDNS IPv6 DNS Sandbox are: 2620:0:ccc::2 and 2620:0:ccd::2.

Internet companies like OpenDNS are promoting IPv6 because the Internet is running out of IPv4 addresses.