Zyxel FTTH box exploration

I have recently received residential FTTH from a provider. To use the service I received a Zyxel box that works as an all-in-one solution offering both IPTV, VOIP, WiFi (802.11ac Wave2) and routing capabilities. The box has a fiber port and the fiber cable enters the residency and connects to that port through a standard connector.

The problem is that this is a very locked down box and is completely managed through the ISP customer site. It offers no local web interface, telnet, or SSH. I want to try and see if I can make it more useful by getting OpenWRT/LEDE on it. I took it apart and found a serial port populated which seems to be standard for Zyxel. It seems to use the Lantiq PXB 4389-720 (GRX330?) and I see references to wave300 and wave400 which I suspect might be the WiFi. Now given that I have access to the serial port I can probably start playing around, but before I do so I would like to make a backup of the current state since this is a rented box I might have to return at some point and would have to return it in the same condition it came. Any advice how to proceed from here? Can I dump the current memory somehow?

Zyxel have good documentation online, try searching for "Zyxel CLI reference guide"

Currently I am stuck at trying to gain access. If I escape the boot sequence I can't get the seed required to generate the password because I don't know what it expects as a parameter and without the password most commands are restricted.

If I do let it boot up completely I get to a shell login, but have neither the username or password to log in. So I am not sure how I can proceed from here.

Not a lawyer here, but if you're renting this from them, you don't own it, and it's probably not within the scope of your contract to modify it... so consider that issue before proceeding, it's up to you of course.

If it's CFE this https://iam.tj/gitweb/?p=cfe_generate_password.git;a=summary should work, if it's not, doesn't hurt to try. Some informations how to proceed with it => http://forum.kitz.co.uk/index.php?topic=13939.0, use cfe_generate_password instead of www.tonycool.es/zyxel/zynpass_en.htm.

Hi @rhyvu ,
Which model of zyxel router do you have? Can you send me a bootlog?