Wednesday, 13 February 2013

PVS 6.0 / 6.1 - Unable to attach to vDisk - Red X - Bnistack Fails

This issue is a real pain. Here we are, thinking that our install has completed correctly and we want to go capture an image but we find we can't attach to the vDisk. I see this a lot in support so I decided to outline below the steps that we use to resolve the majority of these cases.

In most instances you're going to see the following in the Event Viewer System logs:
"The following boot-start or system-start driver(s) failed to load: Bnistack"
This indicates that the BNI driver is failing to load on boot. The most common reasons for this is that we are binding to the incorrect NIC or the driver is being unloaded by another process.

So here are the "quick checks":
  1. Ensure there is no antivirus software installed on the target
  2. Ensure the firewall is disabled on the target and PVS server
  3. If the target is a VM, ensure the NIC on the streaming network is at position 0
  4. Disable spanning tree protocol on the steaming network
  5. Disable IPv6 on the Target/PVS server
  6. If you are using bonded NIC, remove the bond for testing, and re-check
  7. If VMWare targets are being used, ensure you are using VMXNet3 NICS and see my other VMWare Blog post Here
  8. Disable Large Send offload on the Provisioning Server and Target Device:
    Key: "DisableTaskOffload" (dword)
    Value: "1"
Next thing to check is the list of non present devices the OS had banked.
You have 2 options here (I prefer option 2 - setting the variable - as it stays between reboots).

From the command prompt type:


Right-click My Computer.
Click Properties.
Click the Advanced tab.
Click the Environment Variables tab.
Set the variable in the System Variables box.
Value is 1

Once the variable is set head to the Device Manager Click view and "Show Hidden Devices" from the view menu. Expand the "Network Adapters" node and delete any greyed out devices (Intel driver etc below):
Once complete you'll need to uninstall the target device software, reboot the Target and then re-install the target device software again. Run the imaging Wizard and check if you can now image correctly.

If the issue persists open a command prompt and enter fltmc
Ensure there are no filter drivers sitting with higher altitude above the Citrix ones. If there are, uninstall the software to which they belong.

Next look to the properties of the Streaming NIC and ensure that the Microsoft Network Monitor 3 driver is not loading:

So the issue persists? Well head to the advanced NIC Adapter settings to check the Provider Order:
From the Network and Sharing Center, click "Change Adapter Settings" and in the next screen press the "Alt" key. The menu bar appears and you can select Advanced Settings as per the below:

Ensure that the Streaming NIC is the fist listed in the Connection Order
You can disable IPv6 here too if you wish (although not necessary)

Also ensure that the Citrix Provider(s) are listed first in the Provider Order

By now we have covered many bases. If you still see the issue, leave a comment below so we can investigate further.


  1. Hi,
    I am facing the same BNISTACK error with PVS 7.1 and windows 7. I have tried all above instructions

    1. - Ensure that PCI slot number value is same as in link above. Else, I am sure the golden image i.e., the one you converted into vdisk by installing the target software on it, is working fine in vdisk mode and harddisk mode. Make the Golden image boot into harddisk mode, convert it into template or to avod risk, make a clone of it and then convert the clone into template and then create a VM's using that template. These machines will have a same configuration and settings as the working machine and it resolved my case

  2. I am facing the Same BNIStack error on XEN Server 7.0 with the latest PVS 7.9 and I have tried everything under the sun including over a week on with tier 3 Citrix support and we still can't get this working. One thing to mention is we are running XenServer on top of UCS.