FreeVoipDeal, FritzBox and Gigasets

Hi, all. I'm having a VoIP problem which has left me baffled. I am running four DECT handsets off a FritzBox 7590. Three are Gigaset C430s and one is an old Panasonic. Incoming calls are via Andrews and Arnold and outgoing calls are normally routed via FreeVoipDeal.

When I dial out on a Gigaset, the call fails - no message, just no ringing tone and the line eventually clears down. If I then dial a second time (not necessarily the same number or even the same handset), it connects, as do any calls within the next few minutes. After that, the problem returns.

If I route the call via A&A, it always connects first time. The Panasonic connects first time even via FVD.

It looks almost as if the connection with FVD (but not A&A) is going into sleep mode on the Gigasets, but I don't understand how that is possible. I've disabled all power-saving features on the FritzBox and the Gigasets, just in case, but it makes no difference.

I'm sure I'm missing something, but I don't know what. Any ideas? Thanks.

Edited by harb25 (Mon 09-Jun-25 11:46:45)

Sounds like the SIP registration to FVD is not being actively renewed by the Fritzbox.

Have you spoken with Fritz support about it?

Thanks. I had thought about something like that, but I didn't see how that would explain why the problem is only with the Gigasets and not with the Panasonic.

Sorry I glossed over that. Perhaps there is some issue with the DECT profiles in use with the Fritz. Some features and functions for example will be truncated or not available with generic access profiles (GAP) for example…

My setup is similar: 6 assorted GIgaset phones, A&A in, and FVD out. BUT I am using a Gigaset N300A IP, instead of the DECT setup on my Fritz!Box 7530AX. This has always worked perfectly. If you care to post all your FBox DECT settings for the FVD connection, I'll see how these correspond to my N300.

Thanks, but I'm not sure what you mean by 'FBox DECT settings for the FVD connection'. The DECT settings are generic, so cover both A&A and FVD on both the Gigasets and the Panasonic - which is what makes this more puzzling..

Thanks. I've tried enabling the troubleshooting options for DECT, but that didn't help. In any case, I struggle to understand how a DECT issue could affect FVD but not A&A.

That's not the complete picture. In order to set up different VoIP connections you have to fill in relevant data in three sections under Telephony: Telephony Device, Telephone Number, and DECT. It can't all be generic, or you couldn't choose between different I/O options.

You're completely right - I was just querying your request for the DECT data, which is generic.
The Telephone Number settings for FVD are (only enabled options shown):
Username: [my user name]
Authentication name: blank
Password: [my password]
Registrar: sip.freevoipdeal.com
Proxy server: sip.freevoipdeal.com
Country code: Without prefix
Area code: Without prefix
Relay outgoing emergency calls without prefixes
DTMF transmission: RTP or in-band
Provider supports call-back on busy (CCBS) in accordance with RFC 4235
Packet size in milliseconds in send direction: 20
Always register via an internet connection
Contact internet telephony provider via: Only via IPv4
Transport protocol: Automatic
The provider supports encrypted telephony via SRTP in accordance with RFC 3711 and RFC 4568
Media protocol: RTP/AVP
Provider supports MWI (RFC 3842)

Not very useful, as there is little in common between your FB and my N300. Either just differences in naming or completely different ways of setting it up. No help there, I'm afraid.

In reply to a post by harb25:

Thanks. I've tried enabling the troubleshooting options for DECT, but that didn't help. In any case, I struggle to understand how a DECT issue could affect FVD but not A&A.

Suggest you get in touch with Fritz. This may be an 'undocumented feature', that becomes apparent with a mixed estate of DECT handsets and several active VOIP accounts / routing on the box.

Your setup isn't particularly unusual, but its not exactly vanilla either...

The proxy server should be blank according to www.freevoipdeal.com/sip.

Also I would try adding Country code and area code

In reply to a post by harb25:

You're completely right - I was just querying your request for the DECT data, which is generic.
The Telephone Number settings for FVD are (only enabled options shown):
Username: [my user name]
Authentication name: blank
Password: [my password]
Registrar: sip.freevoipdeal.com
Proxy server: sip.freevoipdeal.com
Country code: Without prefix
Area code: Without prefix
Relay outgoing emergency calls without prefixes
DTMF transmission: RTP or in-band
Provider supports call-back on busy (CCBS) in accordance with RFC 4235
Packet size in milliseconds in send direction: 20
Always register via an internet connection
Contact internet telephony provider via: Only via IPv4
Transport protocol: Automatic
The provider supports encrypted telephony via SRTP in accordance with RFC 3711 and RFC 4568
Media protocol: RTP/AVP
Provider supports MWI (RFC 3842)

OK. Thanks for trying.

Thanks for your suggestions. As I understand the FVD setup instructions, proxy server is sip.freevoipdeal.com. Outbound proxy server is to be left blank.
I've tried various settings for country and area codes, and it doesn't make a difference.

Thanks. I've submitted a support request and we'll see what happens.

I use the same setup FB7590 (OS 8.00) with FVD for outbound A&A for inbound.
Two Gigaset A510 DECT phones. All working fine.

Different DECT phones should not make any difference when it comes to call setup etc.

I have a few settings for FVD which are different from yours (only listing diffrences below):

Country code: Without prefix >> With Prefix

Relay outgoing emergency calls without prefixes >> off,
( Emergency calls should go via A&A, they won't work on FVD)

DTMF transmission: RTP or in-band >> Automatic

Provider supports call-back on busy (CCBS) in accordance with RFC 4235 >> off (not relevant anyway)

Always register via an internet connection >> off

Transport protocol: Automatic >> UDP

The provider supports encrypted telephony via SRTP in accordance with RFC 3711 and RFC 4568 >> offf

Provider supports MWI (RFC 3842)

I had some problems with HD Calls (not with the calls itself, but the SIP INVITE messages were getting fragmented and calls would not set up). A bit of a long story, reported this to AVM Support but I don't believe the problem has been fixed yet. So, I turned off HD Telephony. It is under Telephony Devices > DECT phone xxx > Telephony Device Features > Advanced Settings > HD Telephony > HD disabled.

Your problem may or may not be related, but might be worth a try. A&A don't support HD, FVD only on some calls (depending on call destination, i.e. whether it is supported by the onward phone network), so not a big loss turning HD off

When I initially set my own Fritz!Box 7590 up to use FVD, I had some issues. Sadly, I don't recall exactly what those issues were (it's three years ago +/-) but I was in touch with both AVM and FVD. You might try the solution that one or other of those providers offered and thse are my settings which appear to work with Fritz!Fon and Gigaset DECT units:

Account Information

Username ( = me)
Authentication Name {blank}
Password {= mine}
Registrar: 77.72.174.128
Proxy Server {blank}
STUN server {blank}

Country code None
Area code None
[/] Relay outgoing emergency calls without prefixes
[/] Relay special rate numbers without prefixes

DTMF transmission = Automatic
Suppress CLIR = CLIR via RFC 3323 (ID)
CallerID = Disabled

[/] Always register via an Internet connection
Contact internet telephony provider via = Only via IPv4
Transport Protocol = Automatic
Medai Protocol = RTP/AVP
[/] Provider supports MWI (RFC3842)


Note that Registrar line is the IP address for FVD and not the domain name. Apparently on occasion the DNS fails hence use of their IP instead.

Brilliant - you cracked it! Disabling HD did the trick. I'll update AVM Support.
The FVD settings don't seem to make much difference.
Thanks so much for your help.

Thanks for your input. As you can see from my reply to essex_man, disabling HD did the trick.
It looks as if tweaks to the FVD settings don't make much difference, but your suggestion of using the IP address instead of the domain name is helpful.

The background to this is that the SIP Invite message is longer if HD is on (the FB announces more codecs to the SIP server). As a result, the message may no longer fit into one IP packet but is fragmented and sent in separate IP packets. The server should then put these together again.

However, the FB fragments in a very peculiar way and it appears that the FVD server can't reassemble the message again. I reported this to AVM in Feb/March last year but I don't know whether this has been fixed in more recent versions.

Leaving proxy server blank also makes the message shorter but since I got everything to work with HD off, I did not bother to change that as well

Doesn't explain why one call fails and the next one (to the same number, I assume?) succeeds. But good to hear that it has solved your problem.

Thanks for the explanation - it all makes sense. I've updated AVM Support as to what the problem was, so this may add to the pile of tickets they have for the same issue and hopefully encourage them to find a fix.
Doesn't explain why one call fails and the next one (to the same number, I assume?) succeeds.
Interestingly, it didn't matter what the next number was. I could also work round the problem by opening the line first ('dialling tone') then dialling.

>> I could also work round the problem by opening the line first ('dialling tone') then dialling.

That would suggest a problem with DECT (or translation from DECT to SIP signalling).

Have AVM asked for "Support Information" to be sent to them?

Just curious, what OS version is on your FB?

Edited by essex_man (Wed 11-Jun-25 21:26:25)

In reply to a post by essex_man:

>> I could also work round the problem by opening the line first ('dialling tone') then dialling.

> That would suggest a problem with DECT (or translation from DECT to SIP signalling).

As it occurred with the Gigasets but not the Panasonic, the problem must have been in the way that they connect to the FB. Does that make sense, given that disabling HD fixed it?

> Have AVM asked for "Support Information" to be sent to them?

I attached it when I opened the ticket. I've updated them as to the fix and closed the ticket.

> Just curious, what OS version is on your FB?

8.03

In reply to a post by essex_man:

I had some problems with HD Calls (not with the calls itself, but the SIP INVITE messages were getting fragmented and calls would not set up). A bit of a long story, reported this to AVM Support but I don't believe the problem has been fixed yet. So, I turned off HD Telephony. It is under Telephony Devices > DECT phone xxx > Telephony Device Features > Advanced Settings > HD Telephony > HD disabled.

Your problem may or may not be related, but might be worth a try. A&A don't support HD, FVD only on some calls (depending on call destination, i.e. whether it is supported by the onward phone network), so not a big loss turning HD off

Good spot finding this wrinkle. Does the FB enable HD voice by default?

I don’t recall seeing this issue (fragmented SIP invite messages with HD codecs enabled) with other boxes. Something that hopefully FB will remedy in a future firmware update.

In reply to a post by Pheasant:

Good spot finding this wrinkle. Does the FB enable HD voice by default?

I don’t recall seeing this issue (fragmented SIP invite messages with HD codecs enabled) with other boxes. Something that hopefully FB will remedy in a future firmware update.

apparently, it does enable HD voice (as long as the DECT phone supports it).

The IP fragmentation is quite bizarre and I suspect that the FVD SIP server can't reassemble correctly. This was on FritzOS 7.57, not sure whether that was fixed, they did not tell me and the release notes don't mention it either.

Thanks for the intel 👍