Probably no help to the original poster, but I've just migrated to a Fibre connection with Digital Voice.
I also require to retain my own routing set-up so I've configure that to connect to the ONT to allow control of the PPpoE session.

The Fritzbox which is most definitely require for seamless integration to the supplied SIP offering is now a network client.

To enable the SIP client to register on the Zen network, I just needed to forward the usual SIP ports to the Fritzbox.

All is working well.

I can make incoming and out going calls - but there's no audio... so, kinda, but it's totally useless.

Thanks @splidbob

I also have a mesh setup with Asus AX92u nodes and would like to keep it that way.

If I understood correctly, you connected the ONT to your original router - I assume to a LAN port? - and just setup the authentication for the Zen FFTP connection on that original router. Then have your Fritzbox as a client of that original router (connected by ethernet?). Then setup SIP port redirection from the original router to the Fritzbox client?

Thx

Many thanks for this explaination, took awhile but I managed to create the appropriate Outbound NAT Rule on my UniFI Gateway and now inbound calls don't drop after 30 secs. Cheers

Edited by sudman (Sun 02-Mar-25 13:45:16)

Thanks to everyone who posted here - just had my FTTP with DV from Zen installed and thought I'd share my findings with anyone who's still trying to get this working.

FYI - Using my own Cisco Router and Firewall to terminate the broadband, and this worked perfectly fine without any issues. I also have a business contract with a /29 range of IPs.

Confirmed VOIP working with FritzBox directly into ONT.

Called Zen support and they gave out the basic details very readily (Username/Password/Registrar).

Failed to get things working with their help, and ended up giving up - shame really as they spent a long time trying to help, but just defaulted to they only support their box connected to the ONT.

After a long evening yesterday, and long morning today I eventually got things working.

I used the FritzBox as a basic IP Client which picked up a DHCP from my network.
For the phone settings I used the following:

Telephony Provider: Other Provider
Telephone number for registration: Full number with area code
Internal telephone number in the FRITZ!Box: Number without area code (tried with full number and it failed - not sure why)
Username: Full number with area code
Password: As given by support
Registrar: voip2.zen.co.uk
Under Line settings/Location settings check area code is correct

Left everything else as default.

The bigger issue was with NAT. Had to make sure the FritzBox was NAT'd to the highest useable IP address in the /29 range. I also had to ensure that TCP/UDP 5060 was forwarded back to FritzBox (in the end I gave it sole use of that IP as I have 5 others for other services - IE full NAT, not PAT).

Once I'd done that, I could make calls in and out without any issue.

Hope that helps someone else!

Cheers.

So near, yet so far.....

Despite my initial success, it appears all isn't great - had a few minor issues, and some of my family can't call me.

Looks like i'm back to the drawing board...

I've just been on the phone to Zen about this issue and the use of 3rd party VOIP devices or adapters is not supported. If I migrate my phone and BB service to them I would have to keep my telephone service with them for the term of the contract before I could move it to a 3rd party VOIP provider which is a real pain. So I would be stuck with the FritzBox for Digital voice. I use my own Router so would potentially have to live with double NAT. Still researching this but not looking too promising at the moment.

Anyone successfully put their Friztbox on the LAN side with digital voice operational

In reply to a post by mrwrighty:

I've just been on the phone to Zen about this issue and the use of 3rd party VOIP devices or adapters is not supported. If I migrate my phone and BB service to them I would have to keep my telephone service with them for the term of the contract before I could move it to a 3rd party VOIP provider which is a real pain. So I would be stuck with the FritzBox for Digital voice. I use my own Router so would potentially have to live with double NAT. Still researching this but not looking too promising at the moment.

By "not supported" do they mean that their "help" will not assist if there are any queries or that it will not work? If the former, nothing to stop you going ahead as you wish but it is up to you to resolve any problems.

Half the battle in supporting 3rd party VOIP hardware such as a grandstream would be getting the VOIP settings and credentials from ZEN. If this isn't forthcoming then I'm stuck. The actual configuration doesn't faze me, just the availability of such information to make it work.