Administrative Mode Terminal issues…

This was an annoying one. In Windows 2003 you have the Administrative Mode terminal that
allows you to have two standard connection and one “console” connection using RDP (a total of
three (3) concurrent connections).
Well, that is true if the server has not decided to misbehave.

In my case it did. After having two connections to the server (in any combination,console and standard)
the server would not allow a third. Not only would it not allow a third connection but the client also
provided the oddest error message:
image

Once one of the two connected would disconnect all of sudden the server was found again…

So,at this stage I ruled out any concurrent violations,since if it would be a concurrence limitation
I would have expected the following error message:
image

At first, I thought that this might be a networking/security issue of limited RDP connections to this specific
server (no more then 2)…

After some continued digging,researching and registry comparing(with a well behaved server) I noticed a difference
between the two:
HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp\MaxInstanceCount was set
to “2” instead of “ffffffff”

Once I changed the key I had no problem to connect…and thus the mystery of only two administrative connections
(instead of three) was solved…

 

[Now comes the question of how or why was this value changed. The server was a clean installation with SP2 on it.]

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