@begelmir If you look at your config it very similar to what FOG creates if you were to use FOG’s built in dhcp server.
https://wiki.fogproject.org/wiki/index.php/BIOS_and_UEFI_Co-Existence#Example_1
I’m only providing this as a reference.
In the case of your dhcp server its looking to see if the pxe booting computer is bios or uefi. Then its chaining to 10.10.205.100. I assume that system is where your menuing system is. This menuing system could be duplicated in FOG using ipxe instead of grub, but that’s a bit off point.
From a quick check it appears once you enter the grub world it can’t chain load out of grub except for local devices. Maybe your developers know of a way. I don’t work with grub but only at a basic level.
If you could insert the fog server between pxe booting and your grub menu then we can make it work. So the idea is to pxe boot into FOG menu then either have the default FOG menu be your Grub menu or have a menu selection for Grub.
Now that I think about it I made a usb boot menu using grub that connects to FOG. You don’t get all of the features of FOG, but imaging works. Maybe your developers can take this and update your grub menu. https://forums.fogproject.org/topic/7727/building-usb-booting-fos-image
Forum post ordering. I know the ordering took me some time to get use to. Just remember the latest posts are always right under the original post. When looking at the thread above remember this because if the tutorial takes multiple posts the second post in the thread is always at the bottom of the thread.
We can get a solution for you because we have multiple ways to approach this. You just need to pick the path that works best for your network.