Jan 30, 2015

Flashing Movistar Zyxel P870HW-51Av2 with OpenWRT 14.07

Movistar Zyxel P870HW-51Av2 is a VDSL only router which isn't good for where I live but has a good CPU (BCM4350 V3.1 / 400MHz) and an acceptable amount of RAM (32MB) but with a limited flash space (4MB). However, it can get flashed with OpenWRT 14.07.

This router has CFE bootloader which makes flashing OpenWRT very easy using just a web browser. However, I wasn't able to trigger it by pressing Reset button for a few seconds during power on.

The trick to trigger CFE it is by flashing Zyxel unbranded firmware first using web admin console at

After it finishes, flash this corrupted firmware like above to brick it and get CFE prompt afterwards.

When it get bricked you have to set a static IP for your PC (i.e: / and then access

Get openwrt-P870HW-51a_v2-squashfs-cfe.bin from here and flash it. That's all

Just as a reference, I flashed the wrong firmware by accident and it became stuck in a boot loop. I had to try to unbrick it using a USB-to-TTL.

Red is GND ; Green is RX ; White is TX

This was the first time I interact with Zyxel ZLD command prompt. Unbricking was easy. just:




then I sent this file via XModem (using CuteCom under GNU-Linux or TeraTerm under Windows)

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