Unable to PXE boot unknown computer after TFTP transfer error

You might have seen screens like this when PXE booting.

PXEError

It can be quite annoying, especially if it was an unknown computer running from a required task sequence deployment. When this happens you will not be able to PXE boot the computer again, there are to possible scenarios why:

Scenario 1:

Sometimes SCCM creates an Unknown computer object which can be deleted as described in Lars Lohmann Blem’s blog here.

Scenario 2:

At other times the computer object is not created in SCCM and you will not be able to PXE boot it Again, Lars Lohmann Blem also describes the issue on his blog here.

I guess scenario 1 is pretty obvious, delete the Unknown computer object and your computer will PXE boot again.

Scenario 2 is a bit more complicated. I created a small SQL query to list the computers that are unknown but is denied PXE due to the “Last PXE Advertisement” flag.

Run the following query on the SCCM database

select * from LastPXEAdvertisement
left outer join v_R_System
on LastPXEAdvertisement.SMBIOS_GUID = v_R_System.SMBIOS_GUID0
WHERE v_R_System.SMBIOS_GUID0 IS null

You will probably find your computers BIOS GUID and MAC address in the returned data. If you are up for it, delete the row and you should be able to PXE boot the computer Again.

IMPORTANT: This is probably not supported by Microsoft

To delete a row use the following:

This query will list the row you want to delete, it is always a good idea to verify that it is the correct row before actually deleting it. The query should return the row you want to delete.

select * FROM <SCCM DATABASE NAME>.dbo.LastPXEAdvertisement
WHERE SMBIOS_GUID = '<COMPUTER BIOS GUID>'

To delete the row use the following

DELETE FROM <SCCM DATABASE NAME>.dbo.LastPXEAdvertisement
WHERE SMBIOS_GUID = '<COMPUTER BIOS GUID>'

This will verify that the row has been deleted, should return 0 rows

select * FROM <SCCM DATABASE NAME>.dbo.LastPXEAdvertisement
WHERE SMBIOS_GUID = '<COMPUTER BIOS GUID>'

 

 

 

This entry was posted in Operating System Deployment, SCCM 2012. Bookmark the permalink.