_netblocks.dotster.com has no NS records.
NS records for this zone are defined at dotster.com.
NS records for this zone are defined at dotster.com.
Question and response
Question
dig _netblocks.dotster.com. NS
Answer
The response has no answer records.
Authority
dotster.com. 2560 SOA ns1.dotster.com. ops.dotster.com. 1333639566 16384 2048 1048576 2560
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0