iPXE Not Making Requests to Port 4011

[cjs]

On a CentOS 7 system I'm using libvirt with the --pxe option to start a KVM/QEMU VM that will do a network boot. The iPXE banner indicates that it's version 1.0.0+ (6366fa7a).

Libvirt sets up a DHCP server using dnsmasq in a way that makes it rather painful to change its configuration, so I reckoned I'd just set up a second DHCP server (again using dnsmasq) as a "proxy" server listening on port 4011 to provide the boot information that the libvirt DHCP server can't provide, as well as doing the TFTP stuff.

I've got most everything working fine; if I manually interrupt the boot with Ctrl-B and type dhcp followed by boot pxelinux.0 I get into the boot menu I've configured and can load and run stuff.

However, if I let the boot go on in automatic mode it doesn't know to try to load `pxelinux.0` and says "Nothing to boot: No such file or directory" and gives up. I had thought it should try to send a DHCP request to port 4011 to get further boot information, but looking at what's going on with tcpdump this doesn't happen; the only requests I see are DHCP to port 67.

Is there some way, without modifying the configuration of the DHCP server running on port 67, that I can get iPXE to boot without human intervention?