b.riu.edu.ar has no CNAME records.
Question and response
Question
dig b.riu.edu.ar. NS
Answer
The response has no answer records.
Authority
riu.edu.ar. 2282 SOA ns2.riu.edu.ar. hostmaster.riu.edu.ar. 2026012657 1800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0