@dskinner Ok since it DOES work somewhere on your site there is also another possibility that an unexpected dhcp server or proxydhcp server is messing with booting on the same vlan as the fog server. So lets help your network engineers. Lets grab a pcap (packet capture) of the pxe booting process on the same vlan as the fog server. To do this we’ll use the fog server to run tcpdump (packet capture on). This program will capture the dhcp processes of the pxe booting computer as well as the file transfer of the boot loader (ipxe.efi/undionly.kpxe).
I have a tutorial here: https://forums.fogproject.org/topic/9673/when-dhcp-pxe-booting-process-goes-bad-and-you-have-no-clue
You can review the output pcap with wireshark. You can take the pcap to your network engineers, review it your self, or post the pcap to a file share site and either pm me the link or post the link in the forum.
I’ll tell you what you should be seeing. The dhcp process is pretty simple. There is a DHCP DISCOVER packet from the target computer, there is an OFFER from one or more DHCP servers (this is where I would focus, ensure the responding dhcp servers are correct and have the correct settings in place in the dhcp options section), a DHCP REQUEST from the target computer and then finally an ACK from the dhcp server. So this part of the process should only take 4 network packets. If there are more or repeating requests or offers then I would look into that. Once the dhcp process is done then the pxe booting part starts. The target computer will take the name of the boot loader (option 67) and the boot server (option 66) given by the dhcp server and request that file via tftp from the boot server. You should see one initial request for just the file size from the pxe booting client to the tftp server then the client will ask for the boot loader file itself.