u.arin.net has no CNAME records.
Question and response
Question
dig u.arin.net. NS
Answer
The response has no answer records.
Authority
arin.net. 3171 SOA ns1.arin.net. bind.arin.net. 2021113260 10800 600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0