The dns.resolver.query(address, <type>) resolves the address for the query type. The command host looks for A (IPv4 address), AAAA (IPv6 address), and MX resource records when the type is not specified. We specify A, AAAA, MX, SOA, CNAME, NS, SIG, and KEY as the resource record types to resolve the addresses in our recipe. The output indicates that some of these records are not set for the sites that we tested.

The websites that we tested do not contain a SIG, KEY, or CNAME record as we found before with the host -t command. Since we do not have the authorization or the key to actually perform the zone transfer for these sites, this will fail with the message Failed to perform zone transfer. Also note that http://axn.com notes that, there was no answer for the AAAA, thus pointing that no IPv6 DNS record found for the website.