I'm using the component lg.cfc ("Coldfusion Ping, Traceroute,
Dig, Whois Client") from www.maxnoc.com for DNS lookup. I think I
found the component on the tag gallery. It seems reasonably fast
but you'll have to test it and/or put a timeout on the CFINVOKE
tag.
Here's what I ran to isolate the domain name:
<!--- Call lg.cfc for DNS lookup --->
<cfsavecontent VARIABLE="fullresults">
<CFINVOKE
COMPONENT="lg"
METHOD="nslookup"
parameter="#the_ipaddress#"></CFINVOKE>
</cfsavecontent>
<!--- parse out line we are interested in (just domain
name) --->
<CFSET domain_name=REReplace(variables.fullresults,
".*name = (.*).<br>A.*", "\1")>