ns0.es.colt.net has no NS records.
NS records for this zone are defined at es.colt.net.
NS records for this zone are defined at es.colt.net.
Question and response
Question
dig ns0.es.colt.net. NS
Answer
The response has no answer records.
Authority
es.colt.net. 172800 SOA ns0.es.colt.net. dns-requests.colt.net. 2018120600 86400 7200 2592000 172800
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0