sl.telconet.net has no CNAME records.
Question and response
Question
dig sl.telconet.net. NS
Answer
The response has no answer records.
Authority
telconet.net. 900 SOA srv1.telconet.net. hostmaster.telconet.net. 2584 10800 3600 2419200 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0