concursos.oi.com.br has no NS records.
NS records for this zone are defined at oi.com.br.
NS records for this zone are defined at oi.com.br.
Question and response
Question
dig oi.vestcon.com.br. NS
Answer
The response has no answer records.
Authority
com.br. 900 SOA a.dns.br. hostmaster.registro.br. 2026070270 1800 900 604800 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0