/etc/dhcp/dhcpd.conf

subnet 192.168.198.0 netmask 255.255.255.0 {

   range dynamic-bootp 192.168.198.240 192.168.198.250;
   option routers 192.168.198.1;
   option domain-name-servers 192.168.192.2, 192.168.99.2;
   option domain-name "my.org";
   if option arch = 7 {
      filename "/grubnetx64.efi.signed";
   } else {
      filename "/pxelinux.0";
   }
   #filename "/pxelinux.0";
}

subnet 192.168.200.0 netmask 255.255.255.0 {

   range dynamic-bootp 192.168.200.240 192.168.200.250;
   option routers 192.168.200.1;
   option domain-name-servers 192.168.199.2, 192.168.99.2;
   option domain-name "research.my.org";

   if option arch = 00:07 {
      #filename "/efilinux.efi.signed";
      #filename "/grubnetx64.efi.signed";
     # filename "/grubx64.efi.signed";
      #filename "/syslinux.efi";
      filename "/pxelinux.cfg/bootx64.efi";
      #filename "/vmlinuz-3.13.0-24-generic.efi";
   } else {
      filename "/pxelinux.0";
   }
}