_netblocks1.demandware.net has no NS records.
NS records for this zone are defined at demandware.net.
NS records for this zone are defined at demandware.net.
Question and response
Question
dig _netblocks1.demandware.net. NS
Answer
The response has no answer records.
Authority
demandware.net. 60 SOA dns01.salesforce.com. hostmaster.salesforce.com. 2014748893 600 900 2592000 60
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0