sip.dk.telia.net has no NS records.
NS records for this zone are defined at dk.telia.net.
NS records for this zone are defined at dk.telia.net.
Question and response
Question
dig voip06.dk.telia.net. NS
Answer
The response has no answer records.
Authority
dk.telia.net. 86400 SOA dns101.telia.com. dns.telia.dk. 2603222120 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0