Update 2. Although I got OpenWrt to work, I still had corrupted CFE and could not use any asuswrt-merlin firmware. The OpenWrt radio barely works with very low signal levels, so was not an option and I needed to fix the CFE. I managed to fix the router, see this thread for the full details of...
This may be of help for people with broken firmware.
I had problems with my router after doing a factory reset. Turns out some of the CFE default NVRAM parameters were corrupt and the firmware would no longer boot. CFE version is 1.0.1.2. The corrupted CFE parameters prevented recovery mode...
Update: I managed to get the router back with the following steps using CTL-C to get into CFE> prompt and uploading openwrt-15.05.1-brcm47xx-mips74k-asus-rt-n66u-squashfs.trx using tftpd32 on laptop.
ifconfig -addr=192.168.1.1 -mask=255.255.255.0 -gw=192.168.1.2 eth0
flash -noheader...
I believe I have bricked the router, unless someone knows a fix. I started an upgrade to latest merlin version, but forgot to let it complete. According to this link reverting from 3.0.0.4.380_3000 and on is not possible. So it is stuck. The CFE bootloader is still 1.0.1.2. I can successfully...
Update: I am not sure flash1.trx was correct or not, as I was afraid flash0 may over-write the CFE? Read somewhere. However, getting into CFE with quickly hitting CTL-C and setting the eth0 correctly then allowed the mini-web interface to work.
CFE> ifconfig -addr=192.168.1.1 -mask=255.255.255.0...
I followed a similar procedure to recover firmware. I also had to set the Gateway. Connecting serial cable and using putty I could get to the CFE> prompt hitting CTL-C quickly on power up. I then did the following.
Setup TFTPD32 on laptop configured to IP 192.168.1.2. Got to the CFE> prompt...