Internal nodes ping external IP?

Hey there. My developers tell me that they need to be able to ping external IP addresses because they are trying to create an object on one of our servers for a web application that will be used in house, and by our support techs in the field.
We are currently using Proxy 2.0. In house uses an IP address of 192.168.x.x.
In house can use the internet through Proxy, but cannot ping external IP addresses. Proxy handles all of that.
What can I do to give them what they want without an overhaul of what I have?
Thanks!