RemoteApp Disconnected - This computer can't connect to the remote computer.

This problem is "haunting" me.  I had virtually the exact same situation only 2 months ago (entered in EE with the exact same Title...), however, this time the situation is a little different.  First, the only "firewalls" involved are Windows Firewall (built into the Server OS) and some firewall capabilities built into my Zoom Cable Modem router.  I have the firewall in the Zoom Cable modem turned OFF which happened to be the ultimate solution to this problem the last time....of course, this time is different.  I'm getting the same error messages as before, internally from one of my workstations I get:
RemoteApp Disconnected internal to networkexternally from outside of my own network, a user gets:
RemoteApp Disconnected external to networkIf I set the DMZ in the Zoom Cable Modem to the internal address of my server, I can connect to the RemoteApp from within my internal network, but not from outside (externally) of my network.  When I do NOT set the DMZ, and I try to connect to my RemoteApp using the web connection, the internet "cannot display the page" and further diagnostics on the reason why it can't connect showed the following:
Windows diagnostic message from attempted web connectionThe web address displayed is actually my Gateway server and that appears to be my problem at the moment.  Despite having some general connectivity problems this past weekend, I believe that most everything in my Remote Desktop setup is the same as it was before the connectivity problems.  That said, I did have to restore my Server operating system to an image copy I took back in October of 2014 so there is a possibility that I've overlooked something.  Any suggestions would be appreciated.  As I said in my last question on this topic, as much as I really like the RemoteApp capability built into the latest Windows Server operating systems (when they're working), they are always a challenge to get set up correctly and I just have to believe that they should be able to come up with an easier GUI interface (which they may have in Server 2012!?).....
Jim KlocksinOwner, Data ArchitectsAsked:
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bbaoIT ConsultantCommented:
what would happen if you PING the RemoteApp server from inside and outside (once DMZ is pointed to the server on the internet facing modem) by both IP address and host name? be aware i am referring to FOUR situations, please given the results respectively.

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Jim KlocksinOwner, Data ArchitectsAuthor Commented:
To be honest, I didn't understand your suggestion completely, but I did start PINGing both my Gateway server and my Session Host server using their FQDN both within my network and from outside of my network.  The first thing that became evident to me was that my Session Host server (which has 2 NICs and 2 different internal IP addresses) returned the "other" internal IP address of the 2 that I had assigned to that server and, more importantly, the "other" IP address and NOT the IP address that I had entered as my DMZ in my cable modem.  Once I changed the DMZ IP address in my cable modem to the address that was returned from my PING command, the RemoteApp started working both within my network and, as I found out later in the day, it started working from my client's network as well.  Bottom line, your suggestion to PING any and all combinations set up in my RemoteApp configuration, resolved my problem.  Thank you very much.  Now I have knowledge of one more piece of this RemoteAplp puzzle and I'm sure, at some point in the future, I'll run into some other problem.  But I do have to say, again, that I really love the RemoteApp feature built into Windows Server 2008 R2 (as well as their newer Server releases) and, even though I have to pay for an extra domain as well as 2 SSL certificates to make it work for my client, it's worth the cost!  Thank you again for your help on this issue!
bbaoIT ConsultantCommented:
hehe, good to know even a nonsensical suggestion could help. :))

basically the PING way has two purposes: one for connection test to determine if network layer connectivity is as expected, the other for name resolution to determine if correct IP address is in use. you did find out the issue this way.
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