sdns.sify.net has no CNAME records.
Question and response
Question
dig sdns.sify.net. NS
Answer
The response has no answer records.
Authority
sify.net. 3600 SOA pdns.sify.net. hostmaster.satyam-infoway.com. 2000100390 10800 3600 1209601 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0