wwwv21.tum.de has no CNAME records.
Question and response
Question
dig wwwv21.tum.de. NS
Answer
The response has no answer records.
Authority
tum.de. 73731 SOA dns1.lrz.de. hostmaster.lrz.de. 2026022354 21600 1800 3600000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0