Recent web-browsers request IPv6 DNS lookups in preference to IPv4 if they are running on a host with IPv6 enabled. My domain (ipv6.chappell-family.com) has DNS entries for both IPv4 and IPv6 addresses, but defaults to IPv4. This makes it safe for IPv4-only hosts, which make up most of the current web traffic, including search engines, to use the same URL. Browsers running on IPv4-only hosts will not request an IPv6 address and will therefore access the website entirely using IPv4. The landing page, as linked below, attempts to determine whether your machine has a valid globally routable IPv6 address (2000::/3) and whether it is behind an HTTP proxy, by looking for well known HTTP header variables which indicate that this may be the case. Only if the hosts' IP address is determined to be globally routable unicast IPv6 and there are no tell-tale HTTP proxy variables will the landing page offer links to initiate the scan, as encircled in the figure below. | Recent web-browsers request IPv6 DNS lookups in preference to IPv4 if they are running on a host with IPv6 enabled. My domain (ipv6.chappell-family.com) has DNS entries for both IPv4 and IPv6 addresses, but defaults to IPv4. This makes it safe for IPv4-only hosts, which make up most of the current web traffic, including search engines, to use the same URL. Browsers running on IPv4-only hosts will not request an IPv6 address and will therefore access the website entirely using IPv4. The landing page, as linked below, attempts to determine whether your machine has a valid globally routable IPv6 address (2000::/3) and whether it is behind an HTTP proxy, by looking for well known HTTP header variables which indicate that this may be the case. Only if the hosts' IP address is determined to be globally routable unicast IPv6 and there are no tell-tale HTTP proxy variables will the landing page offer links to initiate the scan, as encircled in the figure below. |