Grub2 PXE Boot UEFI MAC address based configuration

[Engelmann Florian]

Dear list,

I am at the same path Andy was:

https://lists.gnu.org/archive/html/help-grub/2013-06/msg00019.html

But I found lots of tutorials describing grub2 using a configuration scheme 
like grub.cfg-01-<MAC>:

https://docs.oracle.com/cd/E52668_01/E54695/html/ol7-install-pxe-boot-uefi.html

http://projects.theforeman.org/projects/foreman/wiki/PXE_Booting_UEFI/8

https://beaveryoga.wordpress.com/2013/08/20/grub2-uefi-pxe-cobbler-ready/

I was not able to make it work. I did:

grub-mknetdir --net-directory=/srv/tftpboot

and my dnsmasq configuration looks like:

interface=eth1
enable-tftp
tftp-root=/srv/tftpboot
dhcp-boot=bios/pxelinux.0
dhcp-match=set:efi-x86_64,option:client-arch,9
dhcp-boot=tag:efi-x86_64,boot/grub/x86_64-efi/core.efi
dhcp-match=set:efi-x86_64,option:client-arch,7
dhcp-boot=tag:efi-x86_64,boot/grub/x86_64-efi/core.efi
#dhcp-boot=tag:efi-x86_64,efi64/syslinux.efi
#dhcp-match=set:efi-x86_64,option:client-arch,7
#dhcp-boot=tag:efi-x86_64,efi64/syslinux.efi
#dhcp-match=set:efi-x86_32,option:client-arch,6
#dhcp-boot=tag:efi-x86_32,efi32/syslinux.efi
dhcp-option=42,10.38.111.15   # Timeserver
domain-needed
bogus-priv
#listen-address=10.38.111.15
expand-hosts
dhcp-range=10.38.111.101,10.38.111.199,12h
local=/xxxxxxxxxxxxxx/

Using /srv/tftpboot/boot/grub/grub.cfg works fine but any file like  
/srv/tftpboot/boot/grub/grub.cfg-01-<client MAC address> is ignored.

Is there any documentation to get the job done?

All the best,
Florian