There is a compiled binary in this repo that can be used to boot a CRS-125 over the network. See http://blog.rchapman.org/post/128621800479/getting-shell-on-a-routerboard for more instructions.
This repo is a fork of the openwrt repo (git.openwrt.org/openwrt.git) with CRS-125 patches added. The CRS-125 patch was written by Charlie Smurthwaite and can be found at http://pastie.org/9872467#6 For more information, see the openwrt forum topic at https://forum.openwrt.org/viewtopic.php?id=48706
-Ryan A. Chapman Sat Sep 12 16:48:02 EDT 2015