mrtg.summitgw.net has no CNAME records.
Question and response
Question
dig mrtg.summitgw.net. NS
Answer
The response has no answer records.
Authority
summitgw.net. 10140 SOA dns1.summitgw.net. admin.summitgw.net. 202412235 3600 3600 604800 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0