@orioliz [Moderator’s note]: I forked this topic, we like to keep issues isolated so that when others find threads they don’t get confused because the subject doesn’t match the discussion.
The short answer here is that you need to install dnsmasq on your fog server to supplement the information you are getting from your dhcp server.
As long as the version of dnsmasq is 2.76 or later then you can use this configuration file for dnsmasq, and once updated will work perfectly.
# Don't function as a DNS server:
port=0
# Log lots of extra information about DHCP transactions.
log-dhcp
# Set the root directory for files available via FTP.
tftp-root=/tftpboot
# The boot filename, Server name, Server Ip Address
dhcp-boot=undionly.kpxe,,<fog_server_IP>
# Disable re-use of the DHCP servername and filename fields as extra
# option space. That's to avoid confusing some old or broken DHCP clients.
dhcp-no-override
# inspect the vendor class string and match the text to set the tag
dhcp-vendorclass=BIOS,PXEClient:Arch:00000
dhcp-vendorclass=UEFI32,PXEClient:Arch:00006
dhcp-vendorclass=UEFI,PXEClient:Arch:00007
dhcp-vendorclass=UEFI64,PXEClient:Arch:00009
# Set the boot file name based on the matching tag from the vendor class (above)
dhcp-boot=net:UEFI32,i386-efi/ipxe.efi,,<fog_server_IP>
dhcp-boot=net:UEFI,ipxe.efi,,<fog_server_IP>
dhcp-boot=net:UEFI64,ipxe.efi,,<fog_server_IP>
# PXE menu. The first part is the text displayed to the user. The second is the timeout, in seconds.
pxe-prompt="Booting FOG Client", 1
# The known types are x86PC, PC98, IA64_EFI, Alpha, Arc_x86,
# Intel_Lean_Client, IA32_EFI, BC_EFI, Xscale_EFI and X86-64_EFI
# This option is first and will be the default if there is no input from the user.
pxe-service=X86PC, "Boot to FOG", undionly.kpxe
pxe-service=X86-64_EFI, "Boot to FOG UEFI", ipxe.efi
pxe-service=BC_EFI, "Boot to FOG UEFI PXE-BC", ipxe.efi
dhcp-range=<fog_server_ip>,proxy
Update <fog_server_ip>
with the IP address of your FOG server and you will be all set. dnsmasq will run along side your dhcp server but not change what it issues. If you turn off dnsmasq then pxe booting will be disabled again on your network.