Then edit your /etc/rc.local
root@OpenWrt:/tmp/speed# cat /etc/rc.local ifconfig eth0 192.168.150.50 ifconfig eth0:1 192.168.1.1 babeld -z 2,30 eth0 ath0 & mkdir -p /tmp/speed dd if=/dev/zero of=/tmp/speed/4M bs=1M count=4 & uhttpd -h /tmp/speed/ -p 80 exit 0
Then at reboot, it should serve a 4MB file on all its interfaces.