slave.silknet.com has no CNAME records.
Question and response
Question
dig slave.silknet.com. NS
Answer
The response has no answer records.
Authority
silknet.com. 3881 SOA main.wanex.net. hostmaster.wanex.net. 2026011502 28800 7200 1209600 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0