ns1.arpa.networklayer.com has no NS records.
NS records for this zone are defined at networklayer.com.
NS records for this zone are defined at networklayer.com.
Question and response
Question
dig ns1.arpa.networklayer.com. NS
Answer
The response has no answer records.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0