New support for NBG6515: overlayfs problem

Dear openWRT community
I am trying to add support for the ZyXEL NB6515 and have created an entry in the TOH. I have been able to boot and flash the generic image for this platform (current 19 release). This boots and have LUCI but neither wireless drivers nor an overlayFS.

I have then followed the instructions ( and built an image for the platform - image was called ....kernel.bin. I could boot and flash it (through tftp, invoked via the serial interface, as typical for several ZyXEL devices). I have also been able to boot from this. There was not LuCi included, but the networking devices seem to work now (from the command line, both serial or ssh).

Is there anything specific I will need to do to define where the overlayFS is stored? How can I configure this when building an image? I suspect I am doing something wrong when building the image. I have so far been using "make menuconfig" / "make".

Any help is highly appreciated.

You mention "PR pending" in the dataentry.
Which pull request exactly (link to PR prefered)?

Thank you for your fast reply; I apologize. I am new here.

I have changed "PR" to 19.07.3 since the system essentially boots this release correctly. As a next step, I wanted to create a usable system image properly but failed (see post above).

I suspect I will need to specify where the overlayfs should be written to. Could you give me a hint what I am doing wrong? Given that I succeed, how could I add the images to the repository?

OK, so when no PR exists, the device would be at best "external image", if you offer prebuilt images for testing for downloading, or if you have a github repository from which other users can build an image.

Otherwise, if now external image or github repository, and no PR exists, the status would be unsupported.

Therefore the question: Do you have prebuilt images to offer, or do you have a github repository?

See the following links:

There is an image in the current release that is bootable / flashable via TFTP.
Unfortunately, also this does not have a working overlayfs, but it is bootable and one can start examining the device. However, it is some sort of support and one can also recover the device with stock firmware back and forth.

The Zyxel NBG6515 is now supported and also WLAN works. It is still a manual installation process but produces a useful device. Preserving the original firmware is essential through a TFTP boot of OpenWrt without flashing (initially).
Detailed instructions are here:

I'm curious if a PR with the current state of support (with non-open source wifi drivers) will be accepted.

I have seen similar instructions on the forum which brought me to the idea. The driver itself is open source, and legally there should not be a problem with preserving a (tiny) bit of binary information present in the original firmware. The instructions I wrote are to copy that missing bit to one's own computer and to save it back to the particular device. I am aware that posting the mtd2 binary information mighe be a violation of copyright laws. Anyone having this router will have access to the mtd2 partition and will be able to save it before erasing it.

I agree with you that this is not really "open source", however, I currently don't see a way of getting it to work in a different manner. If you do, I would be happy to learn how. Any feedback is highly appreciated.

I'm not a developer and not in the position to judge whether adding support for this device in this way would be acceptable or not. Therefore: Try your luck, create a PR or send patches to the mailing list.

Thanks! It seems that there have been comparable issues with this hardware in the past (mt7610e) which were solved in this manner. Since this is the first device I am trying to support I still lack the knowledge to create and present a genuine OpenWrt image or even snapshot. However, using the existing release originally created for the evaluation board (MEDIATEK 7620A/7530) works well with the latest OpenWrt release without modification.

I have also seen supported devices where one needs to modify the image so that it can be flashed (e.g. by faking some control bytes in the image to bypass vendor firmware validation). This is, in a way, the same and has also been accepted, and changing those bytes is not truly open source, either.

I will try to keep working on it. Somehow, I am too stupid to add the device to the TOH... I thought I did that but I did not, obviously.

I have corrected the dataentry now. For future edits, please make sure to edit the dataentry only via the LEFT edit button below the dataentry.

Thanks a lot! It seems I am still doing something wrong. The device NBG6515 does not appear on the TOH page.*%7E%5D=nbg. How do I add it there?

By creating a PR or sending patches that result in OpenWrt firmware image availability on

Thanks. I hope I got it right. I created a GitHub PR and added the link to Correct now?

Hmmm... I couldn't find any PR for NBG6515 on


My apologies (again). I created a repo.
I will read the guide and transfer the contents to a proper pull request.

I saw that my instructions ( to get the device into a semi-working state have vanished. Why is that so? Is there a way to get his page back?

Take a look here:

Thanks! Somehow, this page does not appear any longer when I used the search box to locate it but pointed to an empty page. Now the page appears again when I search for it.

This is just a throw into dark, at best a hint(?) that in the latest official image they use drivers from 2013 (release note). If the build has too new drivers? :slight_smile:
2.4G WLAN code version: mt7620_wifi2716_all_dpa_20130426
5G WLAN code version: mt7610e_wifi3003_dpa_20130301

release note: