Net booting iop32x with RedBoot

[tsuraan <tsuraan@gmail.com>]

I'm trying to get my iop32x-based storage device to boot to a debian
installer.  I've downloaded the various files from
http://ftp.nl.debian.org/debian/dists/squeeze/main/installer-armel/current/images/iop32x/netboot/,
but attempting to load them in the RedBoot prompt gives me these
errors:

RedBoot> load initrd.gz
Using default protocol (TFTP)
Unrecognized image type: 0x8088b1f
RedBoot> load n2100.bin
Using default protocol (TFTP)
Unrecognized image type: 0xa8d315c6
RedBoot> load ss4000e.pkg
Using default protocol (TFTP)
Unrecognized image type: 0x37333138
RedBoot> load vmlinuz-2.6.30-2-iop32x
Using default protocol (TFTP)
Unrecognized image type: 0xe1a00000

For everything but the initrd.gz, that "image type" is the first four
bytes of the file; I have no idea where the image type is coming from
in the initrd.gz.  Which of these files would I be loading for redboot
to start a debian network install?  The "fis list" command shows that
I already have an initrd and a kernel in the flash, but I don't think
that just overwriting those would get an installer running (even if I
could load them, which I can't because RedBoot doesn't recognize the
image types).  Can anybody lend some advice on what I need to do to
proceed?  I had expected some sort of "boot this tftp image" command
the way that PXE booting on x86 works, but I'm not seeing that in any
RedBoot documentation.

Thanks in advance!