Need of iPXE boot in VirtualBox using a ROM with HTTP support

[q2dg]

Hello.
I want to use iPXE to boot a VirtualBox's virtual machine using a ROM which can use HTTP protocol, but what I finally get is a ROM which can use TFTP and some more protocols, but no HTTP. I write you the steps I've done...I don't know what I'm missing:

1.-After fetching iPXE source code as usual (git clone git://git.ipxe.org/ipxe.git) I've commented the line #undef DOWNLOAD_PROTO_HTTP from ipxe/src/config/vbox/general.h hoping to activate HTTP protocol in my compiled ROM (why is HTTP deactivated by default in vbox specific configuration??!!). I've not seen this step anywhere, but I've done this using "common sense".

2.-Then I've made the compilation with the command: make CONFIG=vbox bin/8086100e.isarom ("8086100e" is the vendor_id of the default net card in VirtualBox, the Intel Pro/1000 MT Desktop)

3.-As seen in https://git.ipxe.org/ipxe.git/blob/HEAD:...ox/README, I've replaced the default rom of VirtualBox with my recently compiled one with the command: vboxmanage setextradata "MyVMName" VBoxInternal/Devices/pcbios/0/Config/LanBootRom /home/myusername/ipxe/src/bin/8086100e.isarom

And that's all: iPXE works but HTTP feature is missing, and I don't know why!! I really need it.

Thanks a lot.
Best regards

PD: I use last VirtualBox (4.3.18) in a Fedora 20 x86_64 host machine