ipxe iscsi boot fails, even in virtualbox

Hi,

I set up an iscsi server running iscs-dhcp-server and tftpd-hpa.
At boot I get the following screen:



allow booting;
allow bootp;
ddns-update-style none;
log-facility local7;
default-lease-time -1;
max-lease-time 7200;
authoritative;
option space ipxe;
option ipxe-encap-opts code 175 = encapsulate ipxe;
option ipxe.keep-san code 8 = unsigned integer 8;
option ipxe.bus-id code 177 = string;

subnet 10.0.0.0 netmask 255.255.0.0 {
use-host-decl-names on;
range 10.0.0.164 10.0.0.192;
#option routers 10.0.0.111;

that's my dhcpd.conf

option domain-name-servers 10.0.0.1;
option broadcast-address 10.0.255.255;
option root-path "10.0.0.111:/var/lib/tftpboot/";
next-server 10.0.0.111;
if not exists ipxe.bus-id {
filename "undionly.kpxe";
option routers 10.0.0.1;
} else {
filename "";
option root-path "iscsi:10.0.0.111:::1:iqn.2013-09.at.lightserver.empower:windows";
option ipxe.keep-san 1;
option routers 0.0.0.0;
}
server-name "empower";
server-identifier 10.0.0.111;
}

but however windows 7 doesn't come up, the boot process quits with a bluescreen.
My router is running is OpenWRT. Do I have to set something special to enable iscsi boot?
I found a guide here > etherboot.org/wiki/sanboot/win2k8_iscsi_install < but the rule

iptables -A forwarding_lan -i br-lan -o br-lan -j ACCEPT

brings an error:

iptables: No chain/target/match by that name.

So I checked with ifconfig:

ifconfig
br-lan Link encap:Ethernet HWaddr A0:F3:C1:78:07:C0
inet addr:10.0.0.1 Bcast:10.0.255.255 Mask:255.255.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:8677375 errors:0 dropped:5180 overruns:0 frame:0
TX packets:13955772 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1039227257 (991.0 MiB) TX bytes:17619986844 (16.4 GiB)

Is it very likely OpenWRT is blocking required packet exchange? iptables v1.4.20

best regards