Fritzbox with third party VOIP

Do you think the zen supplied fritzbox can be used with a third party sip voip provider if you are not signed up to zens digital voice? Or is it locked or Zen or automatically overwritted by their settings? Thanks

Yes, no, no.
I have a Fritz 7530AX, a Gigaset N300A, and a few Gigaset DECT phones that are connected to the N300A.
Zen is my ISP.

The N300A supports:
1 landline connection, which connects to the FON port on the 7530AX, for Zen's DV service
1 Gigaset.net connection, which I don't use
6 SIP connections (all via one Ethernet connection to the 7530AX

I have three of the six services configured: Sipgate, FreeVoip, and Zen DV (unnecessary, as it's handled by the landline/FON connection). So I could simply use Sipgate and FreeVoip without subscribing to Zen DV.

I expect that I could use the Fritz box as a DECT base instead of the N300A, but I don't.

Edited by cjn (Fri 04-Aug-23 14:12:23)

I used the Fritzbox with Sipgate and a Dect system. No problems.

I've been using Andrews and Arnold VOIP on my FB7530 for the last two and a half years without any issues. Configuration is pretty straightforward. Just £1.44 per month and I kept my existing number, tech support are brilliant.

I'm glad to see this, and would be interested in any tips, as my attempts to do this using Andrews and Arnold VOIP on my FB7530 keep failing. My broadband - FTTP - is with Zen and very stable but I recently ported the number to Andrews & Arnold as Zen wanted to charge £7.50 a month for a line we rarely use for calls but is still useful to share with people happier to call on a landline.

I've followed the guidance on their site, and it works for while (from 8 minutes to 2 hours) but then fails: with the message; 'Registration of internet telephone number **** failed. Remote site reports reason for error 403'

The Andrews & Arnold helpdesk has been very patient but unable to sort this: they say it could be the router that's faulty, though the Zen service was fine for 2 years. The FrtizBox helpline suggest it's a provider issue as the connection works for a while. I asked Zen if they've any ideas - has the number ported properly? - but (unsurprisingly) they say they can't help.

Can anyone suggest what might be wrong? I've rebooted the router to no avail. I could do a factory reset but fear I'll mess up the home network in the process, despite recording all settings.

Edited by JAPrufrock (Wed 22-Oct-25 17:11:03)

In reply to a post by JAPrufrock:

Remote site reports reason for error 403

A sip error 403, like a HTTP error 403 indicates your request has been received by the server, but the server refuses to fulfil it.

That indicates a A&A problem or possibly a problem with your router. I would think your number has either ported or it has not, there is no halfway house. So when the phone is up, can you ring it? Do you get the correct display number when you ring elsewhere? And are you able to borrow an ATA or an internet phone and try the credentials? Could you try a sip client on your mobile phone?

In reply to a post by JAPrufrock:

I'm glad to see this, and would be interested in any tips, as my attempts to do this using Andrews and Arnold VOIP on my FB7530 keep failing. My broadband - FTTP - is with Zen and very stable but I recently ported the number to Andrews & Arnold as Zen wanted to charge £7.50 a month for a line we rarely use for calls but is still useful to share with people happier to call on a landline.

I've followed the guidance on their site, and it works for while (from 8 minutes to 2 hours) but then fails: with the message; 'Registration of internet telephone number **** failed. Remote site reports reason for error 403'

The Andrews & Arnold helpdesk has been very patient but unable to sort this: they say it could be the router that's faulty, though the Zen service was fine for 2 years. The FrtizBox helpline suggest it's a provider issue as the connection works for a while. I asked Zen if they've any ideas - has the number ported properly? - but (unsurprisingly) they say they can't help.

Can anyone suggest what might be wrong? I've rebooted the router to no avail. I could do a factory reset but fear I'll mess up the home network in the process, despite recording all settings.

I'm with A&A for VOIP. While I have never seen this error message I do sometimes get the account fail to register, but it's usually after there power's been off or the router's been rebooted. Disconnecting the ethernet from the ATA and plugging the cable back in fixes it. Not sure that helps but I thought I'd mention it.

Thanks for the reply:

So when the phone is up, can you ring it? Do you get the correct display number when you ring elsewhere?

Yes, it works as it should when it's live, showing the correct details on my mobile, for example (and in the FritzBox call records). I don't have access to an internet phone (the Fritzbox has paired with 4 DECT phones we already had - they work fine, as they did with Zen). I'll see if I can borrow a suitable phone or try using a SIP client on my phone, though I'm not sure if I can succeed at that

I am sucessfully using a FB7530AX f/w 8.20 , over Zen Fibre, with Sigate, voipfone and a specialist voip connection. Under telephone/line settings I have “ Use a random port for the SIP service of the FRITZ!Box to the SIP registrar” and “ Keep port sharing of the internet router enabled for telephony” both ticked, might be worth selecting, and rebooting FB, as a test?

In reply to a post by nickt:

I've been using Andrews and Arnold VOIP on my FB7530 for the last two and a half years without any issues. Configuration is pretty straightforward. Just £1.44 per month and I kept my existing number, tech support are brilliant.

Same here although only for 11 months in my case and with the AX version of the router.

Have you also noticed on your latest invoice, a not that the price is increasing to "£1.50+VAT from January 2026"?

£1.80 !!!

.

Thanks for the replies - I have now finally got it all to work!

Thanks to the suggestion (above) to try a SIP client on my mobile phone, I used the Android Linphone app which kept connected over several days and strongly implied the A&A service would always work properly for my number with the right equipment.

So I gave up further tinkering with the settings on the FritzBox 7530 - despite several here saying you were using this for the A&A service. I found a cheap eBay used FRITZ!Box 7590 (not the newest version, but running the latest FRITZ!OS: 8.20). It looks as though it might have originally been supplied by another ISP, but anyway, following the relevant A&A help page, it was straightforward to configure and test it.

And it works! Since setting it up yesterday, the telephony connection has remained stable for over 24 hours and the fibre broadband with Zen has been as stable as usual. The Fritz!Box answerphone and missed call messaging work as they should, too.

One quirk, which I found using the Fritz!box diagnostics, was that it seems to disconnect and then reconnect in the middle of the night because the system enabled automatic clearing of the internet connection in the Connection Settings of the FRITZ!Box. It seems the reason is: 'Clearing internet connection briefly to prevent the internet service provider from disconnecting you in the immediate future.' Didn't seem to do any harm, just meant a few seconds downtime, so I've left it alone:

Yes, a recent update for A&A says they will be raising the price of SIP number services, 'brought about by the increase in support burden for these services.... Support of lesser-technical users ... makes it difficult to make the service – originally conceived and priced expecting only highly technical users - profitable, and as many people are reliant on it, we want to make sure it is sustainable so that we can continue to operate it into the future.'

As a kind of semi-technical user - I seem to have contributed to this extra work. Having long ago hear a (highly technical) IT manager praise the A&A service, I now understand why.

Thanks for the update. Pleased you were able to isolate the problem and resolve.

I'm having exactly the same issue with my 7530 AX. I can't work out what the issue is, it connects and works fine but the fails with 403 some time later. A&A say it is t doing the re-register correctly, that is not doing it in a timely manner, I think their default is you must re-register within the hour but this isn't a configurable setting in the FB.

In reply to a post by JAPrufrock:

I'm glad to see this, and would be interested in any tips, as my attempts to do this using Andrews and Arnold VOIP on my FB7530 keep failing. My broadband - FTTP - is with Zen and very stable but I recently ported the number to Andrews & Arnold as Zen wanted to charge £7.50 a month for a line we rarely use for calls but is still useful to share with people happier to call on a landline.

I've followed the guidance on their site, and it works for while (from 8 minutes to 2 hours) but then fails: with the message; 'Registration of internet telephone number **** failed. Remote site reports reason for error 403'

The Andrews & Arnold helpdesk has been very patient but unable to sort this: they say it could be the router that's faulty, though the Zen service was fine for 2 years. The FrtizBox helpline suggest it's a provider issue as the connection works for a while. I asked Zen if they've any ideas - has the number ported properly? - but (unsurprisingly) they say they can't help.

Can anyone suggest what might be wrong? I've rebooted the router to no avail. I could do a factory reset but fear I'll mess up the home network in the process, despite recording all settings.

I am also with Zen FTTP for broadband and A&A for voip - and have been for a few years. I have used Fritzbox 7530, 7530AX and 4050 with the same settings and all have been fine.
The main difference to the settings on the aaisp sitar:

Use telephone number for registration UNCHECKED

Always register via an internet connection UNCKECKED

Also on the Fritzbox Support Page (Click Help & Support at bottom of menu frame, ten click support at bottom of help page):

Upstream VoWifi Prioritization for epdg.epc.*.3gppnetwork.org

Enable Prioritization box ticked.

Hope this helps.

Thanks, that gives me hope but I am still having issues with your suggested settings. Can you let me know what you have in the different fields?

(I have used 01234 567890 as an example in the settings below)

Under the telephone number I have:-

Telephone number for registration: +441234567890
Internal telephone number in the Fritz!box: 567890

Account info:-
Username +441234567890
Authentication name: <blank>
Password: <from SIP password in A&A portal>
Registrar: voiceless.aa.net.uk
proxy server: <blank>
STUN server: <blank>

Telephone number format:-
Country code: None
Area code: None

Relay outgoing emergency calls:=
Relay outgoing emergency calls without prefixes: checked
Relay special rate numbers without prefixes: unchecked
Telephony provider with North American number plan (NANP): unchecked
Relay local telephone number in international telephone number format: unchecked

Use telephone number for registration: unchecked
Always register via an internet connection: unchecked

Contact internet telephony provider via: IPv4
Transport protocol: Automatic

The Authentication Name should be the same as Username.

I think the remainder should be ok.

I e added that as well but still breaking. When I go back in to edit and re-register I notice that the username and Auth fields have the number without the +44 on it for some reason. I edit it and put it back before saving, it registers but then breaks again a while later.

I'm getting close to having to buy a separate QTA device for VOIP which is a pain as I moved away from Zen to A&A to save money!

Right. I suspect the problem may be caused by using the Zen supplied 7530 configured as supplied by Zen. This means it will regularly check in with Zen via TR-069 for config changes/updates and this may be causing the settings to change.
I have never used a Zen supplied Fritzbox in this way. I have always set them up myself from scratch thus removing any unwanted changes emanating from Zen. As Zen use TR-069 to configure their own VOIP settings I strongly suspect this is causing your problem.

Ah, what would the solution be in that case? Is it possible to change some settings around that, if I factory wipe it, would I still be able to connect up to the Zen service? (apologies if daft question)

Actually I can see an option under Internet -> Provider services called "Permit connection to your internet provider over USP (TR-369)"
Looks like TR-369 is a consumer version of TR-069? I wonder if I turn this off it will resolve things...not sure what else might not work though?

Give it a try, worst case you need to change it back.

It won't affect your connection to Zen although it could prevent firmware updates later down the line - not necessarily a bad thing to keep those within your control either.

I have a 7530 AX with Zen and using A+A voip and not seeing any issues.

TR369 is also enabled.

I've been using A&A voip with Zen without any problems for nearly 2 years
The instructions I used to set it up are here

https://forums.thinkbroadband.com/voip/t/4749882-re-...

https://forums.thinkbroadband.com/voip/t/4779535-re-...

Unfortunately that hasn't worked, under the provider services tab there are the following checkboxes:-

Allow automatic configuration by the internet provider:- greyed out and checked, I cannot change this
Permit automatic updates:- unchecked
Observe the URL of the Auto Configuration Server over DHCP and PPP:- unchecked
Permit connection to your internet provider over USP (TR-369):- unchecked

Looks like a factory reset will be in order.

No need for a factory reset. Go into Internet/Account Info then in the top drop down box where it says Zen Internet click on the drop down and choose "Other Provider". Then configure your Zen account settings from there.

I tried both and it still is broken. Even after a factory reset I have the option "Allow automatic configuration by the internet provider
This setting allows the internet provider the secure (encrypted) transfer of the internet account information and login data for internet telephony on this FRITZ!Box. Not every internet provider or internet telephony provider supports this function."

Checked and greyed out so I cannot disable it.

A facrory reset will simply return the router to the state it was delivered in from Zen i.e with the Zen settings applied. The only way to get rid of them is as I said in my previous post - Go into Internet - Account Information and then change the preconfigured "Zen Internet" setting to "Other Internet Service Providor". Give it any name you like then complete the configuration options including your Zen username and password as shown in the welcome pack you would have received. Click "Apply" then when the router completes its configuration you will find that the "Provider Services" tab has completely disappeared.

I tried that earlier but it made no difference.

In the end it's Zen who have flicked a switch at their end via support chat to stop pushing changes to the router and it's now working. It might have been possible to somehow flash the standard firmware from Fritz!box on it I guess but I stopped looking once Zen resolved it. I had to go through support twice though as the first person claimed to have done something which didn't work. It also removes them pushing firmware updates but I can do that manually myself anyway.