Think I found the answer:

When you logon via RDP, “Terminal Services” will contact the domain which 
your account is in to query terminal services information about your 
account e.g. profile path. It does this using RPC to a domain controller.

Taken from here: 
http://blog.rhysgoodwin.com/windows-admin/rdp-though-a-firewall-fails-with-the-rpc-server-is-unavaliable/

In our 3 different AD sites for Domain B, there are different ACLs. In 
Site 1 and Site 2 port 135 is open, from those machines, I can Telnet to 
any Domain A domain controller over port 135. In the Site 3, that port is 
not open between the clients and the Domain A domain controllers. So if 
that really is the issue, I have a few options:

There is a registry value on the client side that I can enable that will 
bypass errors like this (http://support.microsoft.com/kb/815266). I'd like 
to run this by our Security group, to get their take on it. 
We can have the Firewall team open that port up, between the clients and 
the domain controllers.

My only question then is why is this working on Windows 2008 systems? I've 
checked and they don't seem to have that registry value 
(IgnoreRegUserConfigErrors). I'm guessing there is some change that was 
made between the two OS versions regarding this? 


Chris Bodnar, MCSE, MCITP
Technical Support III
Distributed Systems Service Delivery - Intel Services
Guardian Life Insurance Company of America
Email: [email protected]
Phone: 610-807-6459
Fax: 610-807-6003



From:   Christopher Bodnar <[email protected]>
To:     "NT System Admin Issues" <[email protected]>
Date:   10/05/2011 12:58 PM
Subject:        Problem with RDP to W2K3 machines in specific VLANS using 
cross trust credentials



OK, we recently setup a one-way trust between two separate W2K3 forests 
using Selective Authentication. Domain A is Trusted, and Domain B is 
Trusting. Domain B is in a DMZ that spans multiple subnets and sites. 
Everything seems to be working fine so far except for a strange RDP 
problem to W2K3 systems in one of the AD sites in Domain B. Let's say that 
we have 3 AD sites in Domain B (Site 1, Site 2, Site 3). RDP to all 
machines using Domain A credentials works perfectly except to W2K3 
machines in Site3. However I can connect using DameWare to those same 
machines and logon interactively using Domain A credentials. And if the 
system is W2K8, no issues at all. 

The error message is: 

The System cannot log you on due to the following error: 
The Specified domain either does not exist or could not be contacted. 

Anyone run into something like this before? 

Thanks, 



Chris Bodnar, MCSE, MCITP
Technical Support III
Distributed Systems Service Delivery - Intel Services
Guardian Life Insurance Company of America
Email: [email protected]
Phone: 610-807-6459
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