The client machines will be using the proxy to call websites on the subnets. Not all sites have DNS addresses on our local network, so it's easier to just call the IP for the website. So, additional to using the proxy to call, say, google.com they also need to be able to call
http://192.168.3.x (let's say 100 different IP addresses on that subnet) as well as a few more on different subnets.
I can add
http://192.168.3.4 to the proxy whitelist, but what if i need to add 192.168.3.4 through 192.168.3.125? Do I have to add 124 exceptions? I'd rather be able to add a range like the proxy allows me to do for client hosts.