Hi, According to RFC2317 it is permissible to have a CNAME leading to a PTR - for example: $ORIGIN 2.0.192.in-addr.arpa. 1 CNAME 1.A.domain. $ORIGIN A.domain. 1 PTR host1 With a straight PTR https://noc.sixxs.net/tools/ipv6calc/ shows a expected value. However with CNAME and PTR it shows .....ip6.arpa. Other sites (eg. http://www.hart.co.jp/ipv6/ipv6check.php) and linux's host command display the hostname. So are CNAME to PTR permitted with ip.arpa. or the SixXS ipv6calc forgot about it?