tuminfo1.rbg.tum.de has no NS records.
NS records for this zone are defined at rbg.tum.de.
NS records for this zone are defined at rbg.tum.de.
Question and response
Question
dig tuminfo1.rbg.tum.de. NS
Answer
The response has no answer records.
Authority
rbg.tum.de. 3600 SOA tuminfo1.rbg.tum.de. rbg-system.rbg.tum.de. 45944 86400 3600 2419200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0