sigstr.internal has no NS records.
NS records for this zone are defined at internal..
NS records for this zone are defined at internal..
Question and response
Question
dig sigstr.internal. NS
Answer
The response has no answer records.
Authority
. 86400 SOA a.root-servers.net. nstld.verisign-grs.com. 2026030100 1800 900 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0