iweb1.vcn.com has no CNAME records.
Question and response
Question
dig iweb1.vcn.com. NS
Answer
The response has no answer records.
Authority
vcn.com. 10112 SOA ns1.vcn.com. root.vcn.com. 2026021905 10800 3600 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0