ns20.zayo.com has no NS records.
NS records for this zone are defined at zayo.com.
NS records for this zone are defined at zayo.com.
Question and response
Question
dig ns20.zayo.com. NS
Answer
The response has no answer records.
Authority
zayo.com. 1800 SOA amber.ns.cloudflare.com. dns.cloudflare.com. 2398741256 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0