ns2.IPv6.carnet.hr has no CNAME records.
Question and response
Question
dig ns2.IPv6.carnet.hr. NS
Answer
The response has no answer records.
Authority
IPv6.carnet.hr. 7739 SOA ns1.IPv6.carnet.hr. ipv6hostmaster.carnet.hr. 2012071301 10800 3600 2419200 14400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0