How to fix missing PPTP Interfaces from RRAS console in ISA 2006 and stop a memory leak in the process

All PPTP VPN interfaces in ISA 2006 (sp1) disappeared from the Routing and Remote Access Service console, this problem was a cool problem both because it was challenging but also due to the unexpected results and solutions we found.

The first google attempt at finding a solution told us to try the following workaround – Not recommended!

  • Run the following command: C:\> netsh int ip reset c:\resetlog.txt

Well this solution might fix the problem here and now, but you might as well turn to the good old solution of restarting your server every time it fails, because this solution will do the following.

  • Enable DHCP and remove all IP configuration of all interfaces.
    Not the smartest move on a server, and you are stuck with having to retype all your settings again.
  • Most likely the problem will reappear again, since it does not fix the problem.

Now looking deeper into the error, we started looking at event logs – nothing here to help us (let us know if you had any usefull info here for this error). Then we tried various other things, including looking at a snapshot of the memory usage (you can just open taskmgr.exe) and found something surprising. Wspsrv.exe was using more memory handles than all other processes combined on the machine. A memory leak! It has been several years since I ran into a memory leak, it used to be the most common problem for programmers to avoid, but I rarely see them any more.

Memory leak ISA 2006 in wspsrv.exe

What this means is that a program on the machine has some kind of bug that creates a runaway in memory usage, so over time the program uses more and more memory, untill unexpected errors start appearing due to the memory problems.

After some more searching with this new information in hand, we found this Microsoft Knowledge Base article KB973731 with the very telling title “A memory leak occurs in the Wspsrv.exe process when you use the Negotiate (NTLM/Kerberos) delegation in ISA Server 2006” (including ISA 2006 standard, enterprise and sp1)

So now that we know why the error is there, we have also identified some solutions, unfortunately this hotfix is not publicly available, alltough some people have been able to find it with peer to peer services or other means, I would highly recommend getting it from Microsoft directly or thru your Premier Support Agreement or from a consultant with Microsoft Partner status.

We can confirm that installing this hotfix and rebooting the ISA server will make the PPTP interfaces reappear and not have this issue again. Another solution might be not to use Negotiate (NTLM/Kerberos) if at all possible, by choosing either NTLM or Kerberos this problem should not be present.

Did this information help you save time? Please leave a comment encouraging more solutions in the future.

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