chain load with EFI and file:/ URL

[walteste]

I want to use iPXE as a replacement for grub2 on a multiboot system. The goal is to have the BIOS boot in to the ipxe.efi which will read its configuration from a web server. The web server gives it a config file to for instance boot /EFI/redhat/grubx64.efi.

I am stuck at the point where I chainload another efi file. In the iPXE shell I get this:

Code:

iPXE:> imgload file:/EFI/redhat/grubx64.efi
file:/EFI/redhat/grubx64.efi... ok
iPXE> imgstat
grubx64.efi : 1050064 bytes [EFI]
iPXE> boot
Could not boot: No such device (http://ipxe.org/2c048097)

Apparently it can load the file but booting into it fails. Searching for hints using the error code has not gotten me far.

Is this the correct way to boot an EFI file from disk? Is this supported at all?