Found this question via Google and was looking for how to do it via the .config file but could not find that answer here. I've since tracked down the info:
The ipSecurity
element is used by the web.config in IIS7 to restrict access by IP Address. You can use it like this:
<configuration>
<location path="private.asmx">
<system.webServer>
<security>
<ipSecurity>
<add ipAddress="192.168.100.1" />
<add ipAddress="169.254.0.0" subnetMask="255.255.0.0" />
</ipSecurity>
</security>
</system.webServer>
</location>
</configuration>
Update: Note that the role has to be added for this security to be enabled. See the ipSecurity
article linked above.