Troubleshooting PXE in SCCM OSD Part 1

PXE booting makes deploying OS images much simpler for end user technicians. There is a lot that can go wrong though, especially if you're attempting to run it in a high security, heavily filtered network.

In the next few blog posts I'll cover how to go about troubleshooting PXE errors in OSD.

When a PXE failure occurs it helps to be very precise with the step it failed at. The place at which a PXE build fails can tell us where to investigate.

Some possible causes of error in a PXE build are-

• Workstation BIOS configuration and/or lack of RAM
  
• Duplicate SMBIOS id (typically seen on older hardware)
  
• DHCP Server configuration
  
• Network filters / configuration
  
• WDS service failure
  
• PXE service point failure
  
• Wrong collection membership in SCCM
  
• WDS cached collection membership
  
• Obsolete objects in SCCM
  
• Network drivers for Vista/7 are available, but not for XP
  
• Network drivers are not available for Vista/7
  

On the server side there's one log file that will help you immensely. If you have set up the PXE Service Point on the site server it can be found at

%ProgramFiles%\SMS_CCM\Logs\smspxe.log

Or, if you have configured another server as the PXE Service Point it will be found at

SMS_CCM\Logs\smspxe.log

in the root of the drive SCCM is using.

Using Trace32 to view this log file can give you realtime information on the PXE boot process. However, the first error we'll look at won't even show up in this log.

PXE-E51: No DHCP or proxyDHCP offers were received

The most common PXE error I see is PXE-E51. The first indication that something is wrong is when you see DHCP... and you get more than three or four dots.



The PXE process fails at this point with PXE-E51: No DHCP or proxyDHCP offers were received.



This error basically says that the machine can't obtain an IP address. Possible reasons for this include

1. Your DHCP server isn't working
   
2. If you use DHCP reservations you may have made a mistake entering the MAC address of this machine
   
3. You don't have a DHCP pool set up for this subnet, or the pool has no free addresses
   
4. Your DHCP server is on a different subnet and you haven't set up an IP forwader or DHCP Relay agent
   
5. The network cable or port is broken
   

Most of these problems are easy to check, or are easy for your networking people to check. Once the problem is fixed the PXE boot process works properly in most cases. Assuming your network is configured to allow PXE booting this error normally means one of two things - the cable is faulty or there's no DHCP reservation/the DHCP pool is exhausted.

This error highlights the need for preciseness in the error reports from your technicians. Since there's so much more that can go wrong at this stage, it's nice to have an error which is relatively easy to fix.

Troubleshooting PXE in SCCM OSD Part 2
Troubleshooting PXE in SCCM OSD Part 3
Troubleshooting the TFTP Service