vn1.phamanh.id.vn has no NS records.
NS records for this zone are defined at phamanh.id.vn.
NS records for this zone are defined at phamanh.id.vn.
Question and response
Question
dig vn1.phamanh.id.vn. NS
Answer
The response has no answer records.
Authority
phamanh.id.vn. 1800 SOA clark.ns.cloudflare.com. dns.cloudflare.com. 2398844739 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0