I have a couple Server 2008 R2 boxes that, when accessed using RDP over 3G VPN connection, display a black screen.

Couple things that I have noted:

1) When using RDP (same laptops) within the LAN, there is no black screen and it works fine. I feel this rules out the destination servers, as well as the operating system configs on the laptops.

2) I have tried the RDP compression settings fix (group policy), disabled bitmap caching, tried using a lower resolution and tried "control+alt+end, log off and log in again" fix without success.

3) The VPN itself is healthy as well, as the laptop users can access everything else while out of the office using it. It is literally just RDP that is not working as expected.

So, keeping the above in mind, I still feel that its a VPN issue, but specifically around the RDP protocol. As far as I understand it, nothing has been changed on the firewalls, etc and anyways, the connection is reaching the server, it just results in a black screen.

I am stumped. I was thinking it could be the 3G connection, but since the VPN establishes perfectly, and they can access all other services through it (except RDP), I have doubts.

If anyone could help me out or give me some things to check, I will be grateful.


  • What's the latency of the VPN connection like?
    – joeqwerty
    Mar 28, 2017 at 22:06
  • Hi Joe, its around 30ms. Mar 29, 2017 at 9:56

1 Answer 1


I would suggest to check 2 things: 3G may be too slow, so if you can - test with VPN over higher bandwidth connection. As well I would suggest to check MTU is not an issue. VPN lowering MTU for the end to end communication and sometimes network does not allow PMTU discovery by blocking "ICMP fragmentation needed".

  • Hi Alex, thanks for the two things to check. Before I investigate, just want to confirm, will that block cause RDP to fail specifically, and not other protocols that are being used (https, imap, SMB, etc.) ? Mar 29, 2017 at 9:59
  • Mtu is a problem for other protocols as well. Speed I think may be more issue for RDP than others Mar 29, 2017 at 10:21
  • Other protocols aren't as sensitive to network issues as RDP nor is it as noticeable when there are network issues. You might try something like video/audio streaming while connected to the VPN to see if there is any noticeable lag, stuttering, buffering, etc. If so, that may be another indication that the VPN is the cause of the problem.
    – joeqwerty
    Mar 29, 2017 at 10:31
  • Thank you very much Joe and @alexlev2004 - will check it out and report my findings. Mar 29, 2017 at 11:12

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