PXE issues

[Jamaal]

Hello all,

I’ve been having some PXE issues at work and tried what I could, but things are not working out correctly. Here’s what going on and I searched throughout the internet and can’t get it.

The FOG version I have is 1.5.10.1754, kernel 6.12.35 for both 32 and 64 bit.

We have some HP desktop computers that have the generic network card (11) 1219-LM.
A model that’s giving issues for example is a HP mini ProDesk 400 G6. Not that it matters, but it has an i5 processor.

I finally talked some sense to our IT admin to use FOG instead of MDT (snail). Anyway,
he has the WDS server disabled. We have a Windows Server 2022 that has DHCP server enabled.

When I boot the mini via PXE, it flashes back to the boot menu like it doesn’t see FOG.
If you go to the BIOS and select F6 (some PXE test mode I think), it wants to PXE from the disabled WDS server and shows the boot file it wants to boot from instead of FOG. It happens to an older HP ProDesk 400 G4 with the same 1219-lm network adapter. It shows its Ip address. As a test, I asked him to re enable the WDS server yesterday and it pxe with no issues.

If you put a HP Mini that’s an i7 (I believe a HP Pro Mini 400 G9) that has the same 1219-LM network adapter, it sees FOG and it’s ready for registration.

I double checked and triple checked DHCP is setup correctly on that vlan, ex; correct fog server name and file is ipxe.efi, even created the policy for the pxe arch to 0007 and 0009.

I tried downgrading to different kernels, but didn’t fix neither.

I’m at a loss on what else to try because WDS is very slow and I don’t want to keep using it to slow us down as we have MDT with it deploying Windows 10 and having to upgrade to Windows 11 with a PowerShell script. I was thinking about reinstalling FOG, but not sure if that would help.

Again, thanks for your guys support for all theses years.

[george1421]

@Jamaal This problem is solvable but it make take some effort on your part.

Lets start with the basics.

For the DHCP IP zone where your pxe booting clients live, you need to set dhcp options 66 to the IP address of your fog server. And for dhcp options 67 that needs to be snponly.efi or snp.efi. With those settings configured on a MS Windows based dhcp server a pxe booting client should boot. Make sure on your dhcp server that is responding to bootp and dhcp requests. Its been a while since I messed with windows but on the dhcp server there should be a setting of dhcp bootp or both. Select both.

Now lets talk about WDS for a second. A WDS server can use dhcp options 66 and 67 as above, but it can also run a proxy dhcp service that tells the client to ignore the dhcp options and come talk to it for boot information after it gets an IP address for the dhcp server. This maybe called a netboot service or something like that on your WDS server. Its not part of the main WDS service. If this service is still enabled it will override any settings you make in dhcp for pxe booting.

So how do you figure this out to what’s wrong?

The easiest and most complicated issue is to identify what is flying down your network during the pxe booting process. You can do this with wireshark on a witness computer (computer not part of the pxe booting process). This witness computer can either be a ms windows or linux computer, the key is to have wireshark loaded. When you start up a capture use a capture filter of port 67 or port 68 or port 4011 That will limit what wireshark sees to only the dhcp packets. Make sure the witness computer is connected to the same subnet as the pxe booting computer.

Start the packet capture and then attempt to pxe boot the target computer. Continue to capture the packet until the pxe booting computer either reaches the fog iPXE menu or errors out. Then stop the capture.

In the top section you should see the DORA (discover, offer, request, and finally ack/nack) process. The process goes as follows:
Client -> Discovery
Server-> Offer
Client -> Request
Server -> Ack/Nack

In this process you are most interested in the one or more OFFER packets. In a normal network you should only see one OFFER packet. When WDS is involved you will see one OFFER packet from your main dhcp server and a second OFFER packet from your WDS server. If you are seeing the OFFER from your WDS server then you don’t have the proxy-dhcp service disabled, and that is causing your issue. If you are seeing two offer packets from two different dhcp servers, such as a primary / secondary setup make sure both dhcp server are configured to boot from FOG server.

Now what do you do if you only have one OFFER packet and its still not working. This is where you need to select the OFFER packet and then look at the data in the parameters box. There will be the bootp fields of next-server and boot-file these need to be configured for the fog server IP and snp.efi. Then in the dhcp options section options 66 and 67 need to be set correctly. If one or the other sections are not set correctly you will get random machines not booting while others are.

If you can’t figure it out save the packet capture file “be sure you only captured the dhcp process” and up load the file to a file share site and post the link here and one of us will take a look to see what’s wrong. But I think from what I covered here you should be able to figure out what the pxe booting client is being told to do incorrectly.