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Cisco VPN with Windows 7 (ndis.sys BSOD)

After giving it much thought, I recently upgraded our first enduser to Windows 7. Having used Windows 7 (64-bit) for over a month with not many issues you can imagine my surprise when the user's laptop kept bluescreening after disconnecting from the VPN. On average it would bluescreen about 50% of the time just after I clicked disconnect. The error would report that ndis.sys was the root of the problem.

After researching the issue online I could only find information on the more popular Cisco IPSec VPN client and not the Cisco AnyConnect client. Also, the issue they were facing was related to the computer going into a bluescreen cycle after installing the Cisco VPN client and rebooting. My laptop would reboot sucessfully and never have problems until I tried to use the VPN.

I found several websites which gave workarounds, but no real solutions. Eventually I found an article that mentioned if you install a DNE update it would correct the problem. I try to not post anything on here that's redundant and to only post information that I've had a hard time finding on the Internet. While his article is accurate and did fix my problem I felt it could be improved upon in two ways. First, I couldn't find any articles that mentioned the AnyConnect client. Everything was referring to Cisco's more popular IPSec client. My tests were done using Cisco's AnyConnect version 2.4.0202 (the latest version at the time). Additionally, the article I read stated you needed to manually delete two files related to ndis.sys and then do a Windows repair using the installation media to restore those files after installing the VPN client. Citrix has since updated the process and made it much easier. Below are the steps I followed which took care of the problem.

  1. Uninstall your Cisco AnyConnect client.

  2. Reboot

  3. Go to Citrix's website to obtain the winfix.exe and dneupdate.msi. (Cisco uses DNE which was developed by Deterministic Networks. Citrix bought Deterministic Networks.)

  4. Run winfix.exe to automatically correct the files that the other article manually instructed you to edit. Once complete it will prompt you to reboot.

  5. Run dneupdate.msi to update DNE, which is what's causing the BSOD.
  6. Reinstall the Cisco AnyConnect client.

While I was only able to test it on one machine, it did successfully fix my problem and by looking online it looks like it has fixed many others. As we deploy more Windows 7 machines I'll be sure to edit this post if I run into any problems with this process.


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