f.nic.RS has no CNAME records.
Question and response
Question
dig f.nic.RS. NS
Answer
The response has no answer records.
Authority
nic.rs. 900 SOA a.nic.rs. hostmaster.nic.rs. 2026021561 14400 3600 604800 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0