filter.localtel.net has no CNAME records.
Question and response
Question
dig filter.localtel.net. NS
Answer
The response has no answer records.
Authority
localtel.net. 1702 SOA ns1.nwinternet.com. hostmaster.nwinternet.com. 2026022000 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0