sv2dns01.equinix.com has no NS records.
NS records for this zone are defined at equinix.com.
NS records for this zone are defined at equinix.com.
Question and response
Question
dig sv2dns01.equinix.com. NS
Answer
The response has no answer records.
Authority
equinix.com. 3600 SOA dns1.p07.nsone.net. hostmaster.nsone.net. 1654242508 10800 900 864000 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0