dns2.viettel.com.vn has no NS records.
NS records for this zone are defined at viettel.com.vn.
NS records for this zone are defined at viettel.com.vn.
Question and response
Question
dig dns2.viettel.com.vn. NS
Answer
The response has no answer records.
Authority
viettel.com.vn. 1800 SOA dns1.vietel.com.vn. admin\@vietel.com.vn. 2025103101 10800 3600 604800 1800
Additional
. 0 OPT ; payload 512, xrcode 0, version 0, flags 0