Fix PXE Boot crashes WDS during SCCM OSD

In this post, I will cover the solutions to the problem where PXE boot crashes WDS during OSD in an SCCM environment. You can try these suggested solutions if WDS is repeatedly crashing during PXE boot.

In Configuration Manager, PXE boot WDS and PXE responder are two methods for booting devices using PXE and out of the two, the PXE responder works efficiently. Many organizations still use WDS and configure DHCP options 66 and 67 for PXE boot to work.

During my consulting, I normally come across troubleshooting questions related to PXE issues for most organizations. If you visit Prajwal Desai Forums, you will notice that common complaints are PXE boot failures, clients failing to get IP addresses from DHCP, PXE responder service issues, weird PXE boot errors, and much more.

What happens during the WDS crash?

So let’s say you use a Pre-Boot Execution Environment distribution point to PXE boot your client devices. What’s intriguing is that the PXE boot works initially, but then the process stops running. When you examine the PXE logs, you’ll notice that the WDS service has crashed.

Whenever WDS crashes on a DP, ConfigMgr administrators choose to restart the service and resume the OSD. However, in this case, I can tell you that restarting WDS on the server doesn’t resolve the issue. Even if you try, after a few minutes, WDS crashes again, leaving the OSD to standstill.

Why does PXE Boot crash WDS during SCCM OSD?

The common reason why the SCCM PXE boot crashes WDS during OSD is due to the presence of redundant backup routers in the setup.

If the network administrator has set up the IP Helpers for PXE (DHCP relays) on both the primary and backup routers, two duplicate PXE request packets are sent to WDS. First, the original PXE request by the primary router and a duplicate PXE request by the backup, redundant router.

In such cases, the duplicate PXE request may overwrite or replace some information in WDS from the original PXE request. This issue causes information in WDS for the PXE request to become corrupted, and hence the WDS crashes.

Alright, let’s look at resolving this issue now. If the Windows Deployment Services (WDS) is crashing due to Pre-Boot Execution Environment (PXE) boot in a Configuration Manager environment, you can try the below-mentioned solutions.

1. Disable the PXE IP Helpers in the backup router

To fix the WDS crashing during the PXE boot, you must disable the PXE IP Helpers in the backup router. This will ensure duplicate PXE requests are not sent to the client from this router.

To disable the PXE IP Helpers in a backup router, locate the redundant DHCP IP Helper entry and add an entry with the IP address of the PXE server. This must be done by your network staff or someone knowledgeable in router configuration.

2. Change WDS provider from multithreaded to single-threaded

Configuring the Configuration Manager WDS provider to be single-threaded instead of multithreaded is another possible solution to the problem of PXE boot crashing WDS. This configuration will prevent the second, duplicate PXE request from interfering with the first request and limit WDS processing of PXE requests to one at a time.

Here’s how you can configure the Configuration Manager WDS provider for single-threading:

1. Sign in to the distribution point server that is enabled with WDS.
2. Open the registry editor and navigate to HKEY_LOCAL_MACHINE\Software\Microsoft\SMS\DP.
3. Create a registry key with the name ‘NumberOfThreads‘ and set the DWORD value to 1.
4. Restart the distribution point server to apply the changes.

Conclusion

I hope the solutions listed in this article helped you to resolve the WDS crashing issue during PXE boot. If you need further help with this issue or other ConfigMgr issues, take a look at our SCCM community forum.