x-drum

Add the following chunk to your existing ISC dhcpd.conf file.

if exists user-class and ( option user-class = "iPXE" ) {
    filename "http://boot.smidsrod.lan/boot.ipxe";
}
else {
    filename "undionly.kpxe";
}

(or see https://gist.github.com/4008017 for a more elaborate setup

x-drum

ddns-update-style none;
deny bootp;     #default
authoritative;

include "/etc/dhcp/ipxe-option-space.conf";

# GREEN
subnet 10.1.1.0 netmask 255.255.255.0 {
        range 10.1.1.100 10.1.1.199;
        option subnet-mask 255.255.255.0;