We have a plugin installed on our site called Restricted Site Access. It redirects all users to a "restricted" page unless their IP address has been added to the back end.
[login to view URL]
Right now we are able to enter single IP's, and IP ranges into the admin backend. We need the code of this plugin to be edited and extended to allow for the use of IP addresses that use wildcard * delimiters. So for instance IP's like: 192.168.1.* and 192.168.*.*
I have demo site set up that is a clone of the live site where development can be done. However the plugin will have to be download and installed on the live site, and working, by me.
Please let me know if you have any questions.