[syslinux] syslinux 6.03pre17 + gpxelinux.0 + iso from http not working

[Ross, Matt]

Hello,

I am running Debian testing x64 and have manually installed the 6.03pre17 deb packages for extlinux, pxelinux, syslinux, syslinux-common, syslinux-stuff and syslinux-utils.

I have a working tftpd-hpa 5.2-18 PXE system and can boot PCs to it. All .c32 binaries, gpxelinux.0 and memdisk are from the Debian packages and everything works except for http/https sources of ISOs. I have tried both of the following and many combinations gleaned from other people's work:

LABEL util1
   MENU LABEL ^Util1
   LINUX memdisk
   APPEND iso
   INITRD http://ourserver.ourdomain.com/Software/Util1.iso

LABEL util1
   MENU LABEL ^Util1
   KERNEL memdisk
   APPEND iso initrd=http://ourserver.ourdomain.com/Software/Util1.iso

When selected a message briefly appears saying:

Loading memdisk... ok
Loading http://ourserver.ourdomain.com/Software/Util1.iso...failed: No such file or directory

Syslog on the PXE server says:

in.tftpd[30574]: RRQ from xxx.xxx.xxx.xxx filename memdisk

The web server hosting the ISO does not have any record of a download attempt. Please can someone tell me if I'm missing something obvious?

Regards,

Matt