Not entirely sure what the question is, but sometimes with proxy situations you can modify the /etc/hosts file (or equivalent) to make the machine resolve itself as a external host to play nice as a proxy when the external world thinks otherwise (or similar trickery)

This also supersedes in most configurations a dns lookup so there is no need for runing internal and external dns servers until the /etc/hosts file needs maintaining because of the number of proxies your running or something.