Thank you! We currently use TMG as a reverse proxy to publish lync and OWA and we are planning to publich these services via MWG which is configured as explicit proxy so I'd like to know why such configuration is not recommended. Also, I would appreciate sharing me any hint or document or URL that can help me configure both forward and reverse proxy on a single appliance.
One of the reasons I personally wouldn't recommend it, is there is no documentation on setting it up that way even though it is technically possible and will work just fine IF set up correctly and properly sized. Another reason I don't personally recommend it is that it will likely make your ruleset and configuration unnecessarily complicated and hard to manage without error. Often the people administrating reverse proxy are not the same people that are administrating forward proxy, so there is that to consider as well. Lastly there is the loading issue, big spike in load in one direction could impact performance in the other. Of other note is I believe TMG does more than just reverse proxy where OWA and Lync is concerned so you may have some challenges with that piece. Lync (especially Lync for Business, formerly Skype), I doubt you will be able to do anything but port forward that traffic. Highly recommend doing some research and testing on reverse proxy for those protocols before even considering running on same box as forward proxy. Just my two cents. There may be other opinions and comments coming from others.