Sunday, August 22, 2010

An authentication error has occurred. The specified target is unknown or unreachable. NLA Error, XP SP3

This is really annoying and it took me a little while to find the fix, so I am blogging about this in hopes that others waste less time!

I have a 2008 R2 RD Session Host server farm. IT is set to accept only connections from NLA clients.
Connecting from any Win7 machine works great.

Then I tried to connect via a client running XP SP3, running RDC 6.1 (supports NLA) with CredSSP enabled.

I got the following error: An authentication error has occurred. The specified target is unknown or unreachable.

If I turn off requiring NLA on the farm servers, I can connect.
Next, I added RDC 7.0 and tried again. I get the same error. 
I tried from more XP clients, with the same setup and I get some that get in and some that give the error.  VERY CONFUSING.

Turns out,  there is a hotfix out there that fixes this:
I added:, and rebooted.   
Now it works.

What I find interesting is that the hotfix does not specifically lay out this exact error result.ARGH.If it had I would have found it SO much faster.

Note: WebSSO will still not work unless you have RDC 7.0 on your XP client - RDC 7.0 is a requirement for WebSSO.  


  1. Thank you so much for posting this! It saved me hours and hours of research!

    1. This comment has been removed by the author.

  2. Thx, still valuable after all this time :-)...

  3. Thank you for this. Saved a lot of time

  4. I am so glad there are people like Kristin Griffin in the world. Why just today, this problem came up for us here at my organization and this article solved it for us. Now we can use NLA for our legacy Terminal services clients. Then I realized who it was that wrote the article and I thought WOW, I think I know her

  5. heheh. Hi DARTH - yes as it turns out we do know each other! ;) Glad I could help!

  6. I tried to connect but it displays this message: the remote computer requires Network Level Authentication, which your computer does not support. For Assistance, contact your system administrator or technical support.
    My operating system is Windows 7 Home Premium and my RDP version is: Control version 6.2.900.
    My RDP has NLA Supported.
    I tried from other operating systems and shows me the same message.
    Do not know what to do...
    Please help me.

  7. many thanks, i was confusing to find out the description and failed, finally i found this blogs and fixed this issue, many thanks once again to Kristin

  8. Thanks for bridging the gap between the error message and the fix!

  9. Thanks so much...this worked for me.