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LuxFibre disables alternative VoIP services?


UPDATE: Recent Fritz!Box OS allow to choose between Internet or Voice VLAN when configuring VoIP accounts. See AVM provides workaround to use 3rd party ITSPs. The statements below are obsolete.

Yes it does, unfortunately.

So why exactly? The short answer is, because the VoIP part of the Fritz!Box is moved to an isolated virtual LAN (VLAN) with no Internet access, so the Fritz!Box VoIP part cannot reach any alternative VoIP services as these are somewhere on the Internet.

But why is this necessary? The LuxFibre product is designed to provide all services over IP. This includes any telephone services (analogue, ISDN) which were previously delivered directly via copper. Telephony over IP cannot deliver the same quality and availability out of the box as traditional telephony services. The regulation however requires all operators to provide the same level of quality and availability on telephony over IP services, hence the requirement to differentiate services on the LuxFibre product. EPT selected the way of 1 VLAN per service:

  • Internet access VLAN 35
  • Voice VLAN 39
  • TV VLAN xy
  • etc

Using different VLANs makes it quite easy to prioritize one VLAN over another and to configure guaranteed bandwidth. By these means EPT can meet the regulatory requirements for quality and availability of their Telephony service. Additionally as all the services are produced within the EPT network, none of the VLANs need to provide Internet access (except for the Internet access VLAN itself). So the Voice and TV VLANs do not provide any Internet access at all. This also allows EPT to completely isolate their VoIP and IPTV systems from the Internet, hence protecting the systems themselves but also the users from being attacked. The Fritz!Box supports this kind of setup by allowing the usage of different VLANs for the different services provided via the Fritz!Box. The sad thing about it is that you cannot select the VLAN per VoIP service but only for all VoIP accounts.

The consequences are that you can either use your EPT VoIP service or reconfigure your Fritz!Box to support all other VoIP services beside EPT, but you can never run both from the same Fritz!Box.

A common work-around is to use your old Fritz!Box (in case you had one prior to ordering LuxFibre) and connect it as a client behind your LuxFibre Fritz!Box (aka P&T HomeServer). The 2nd Fritz!Box will use the regular Internet access just like any other device you connect to the Fritz!Box (e.g. PlaySation, Wii, Laptop, etc). You could even daisy-chain your EPT VoIP Service via the S0 (ISDN) interface on the P&T HomeServer to the second Fritz!Box, giving you access to all your telephony services from any phone connected to the 2nd Fritz!Box.

Another work-around is the usage of VoIP telephones (e.g. Gigaset IP DECT), as before you may even daisy-chain your EPT VoIP service via the FON1 (anlaog) in case the chosen telephony support an analog line.


  1. Ok, If I understand well,it will not be possible to configure one DecT phone to receive calls sent to a VOIP number from EPT and send calls from a number of another provider. I can only configure a dect phone on my main fritzbox to work only with EPT voip and other dect phones on a second fritzbox configured with another VOIP provider. Am I correct ?

    • Yes that’s it. However instead of forwarding the EPT Telephone signal to a DECT phone, you can send it to the S0 (ISDN) or the FON1 or FON2 port and connect your 2nd Fritz!Box or a Gigaset with ISDN or analog port to the 1rst Fritz!Box just like you would connect a traditional phone line to a Fritz!Box or Gigaset. You may then use your alternative VoIP accounts as VoIP account on our 2nd Fritz!Box or Gigaset and use your EPT VoIP just like a PSTN service from the very same device. It’s difficult to describe this in words, I might create a diagram if I get the time.

  2. Thanks for the solution. It is clear. In fact I will get the same fonctionality as before, but from the second fritzbox. And my EPT VOIP will appear as analog or isdn on the 2nd fritzbox.

  3. Hi

    I came across this blog while I was looking for info, having requested LuxFibre30 and wanting to prevent troubles.
    I currently (LuxDSL) have along with my ISDN installation (one DECT base and several handsets) also three IP LinkSys phones, registered to Betamax’s SIP server.
    Do you mean that P&T will impose one VLAN per VoIP traffic dedicated originally for regular voice calls, and that way I could not anymore use Internet access VLAN 35 for my IP phones?


    • Hello Antonis,

      the restriction only applies to VoIP services provided from within the Fritz!Box itself. It does not apply to VoIP devices connected via Ethernet to the Fritz!Box, such devices are handled just like a PC or a game console or any other network equipment. So as long as the DECT base supports SIP itself and does not rely on the Fritz!Box to convert ISDNSIP you won’t have any issues. The Liknsys phones will work as usual.

  4. Great.

    Thanks a lot. I unfortunately could not find these on the avm doc (not sufficiently detailed as by other networking brands).
    As far for the double NAT (to escape it), they promised me a public dynamic address for free, as with LuxDSL.
    It remains to follow the IPver6 developments, as I understand, soon (a couple of years) it will become compulsory.

    Thank you Marc.

  5. Bad news, I am afraid. The Fritzbox, can only create VLANs according to the QoS, therefore VLAN 39 will contain also VoIP traffic coming out from the IP phones.
    Only workaround is a level-3 fast ethernet switch (WLAN->DSLAM) to assign VoIP traffic destined to a specific public internet host to VLAN 35. The P&T’s description states clearly:
    4.2. Layer 2 configuration
    As the interface is an Ethernet interface, the layer 2 configuration is also based on
    Ethernet and the traffic separation (High Speed Internet and Voice) is done via the two service VLAN’s (IEEE 802.1q).
    VLAN 35 is used for the High Speed Internet traffic, and VLAN 39 for the Voice. The HAG needs to tag the traffic based on the service.
    So, it won’t work!

    • Hello Antonis, I’ll have to lookup information about Transport Layer based VLANs on the AVM Fritz!Box. However it’s possible that this is a new option activated by the customized Fritz!Box configuration used by EPT. Regards, Marc

  6. See for yourself (received from their support) that it is NOT a EPT’s configuration trick. In fact, EPT would certainly have to separate the two situations, telephony-destined datagrans and public internet-destined ones, thus the need to double NAT, as to keep telephony traffic to a totally isolated network. If the AVM’s box has a switching engine, then a layer 3/4 switching modification would make the trick. I quickly browsed Cisco, HP and Netgear hardware, and I suspect that only a modular, sophisticated $,$$$ box could at the same time be L3-switch, VDSL router and integrated VDSL-modem (PPPoE). Obviously not any simple customer’s situation…


    • You’re reasoning is not wrong, however the Fritz!Box runs Linux 2.6. It’s actually a very customized linux 2.6 kernel but you can still do a lot of things for free (well for the cost of a Fritz!Box).

      I now also recognize where your text comes from. It’s the technical description of the Ethernet interface provided by the optical network termination equipment to the Fritz!Box. It does however not describe the internal behavior of the Fritz!Box. VLANs are not extended into the internal routing of the Fritz!Box, they are used to provide 2 WAN interfaces to the Fritz!Box within 1 single physical RJ45 Ethernet plug.

      The previous behavior of the Fritz!Box (and I will try to confirm this is still the case) was to attach the VoIP Daemon statically (via a configuration parameter) to the (virtual) WAN interface VLAN39, while anything else is attached to the (virtual)WAN interface VLAN35. The Fritz!Box was not providing Layer4 based routing, only some kind of source-based routing, eventually process-owner based routing.

      Also there is no technical need for NAT44 (double NAT) in general. The possibility to order a public IP address at cost documents this very clearly. (There are other ways to proof this, but I’m lazy and I’ve chosen the shortest way). Although, address conservation might be a political reason for NAT44.

      For a even better understanding, can you confirm you actually tried to use an external VoIP device connected via to a LAN port of the Fritz!Box?

  7. Here the screendump I got from AVM:
    The Interface Description document is stored on the P&T server (telecom->operators->documents->interfaces).
    I talked to the phone with some EPT’s people to confirm that no test installation is available to test one of my IP phones. They also promise a free dynamic public address, should my ftp server not function, but I don’t dare to order an installation before previously testing it. In between, the support people of AVM are unable to give me accurate answers, and proposed me to write a request to their presales people, which I did.
    If the VLANs work like you wrote, then VoIP traffic must be bridged to VLAN 39, not?
    I home AVM will answer.


    • OK, so you have not yet confirmed that the Fritz!Box works differently than what I already confirmed previously. The screenshot provided shows the configuration element responsible to bind the Fritz!Box’s internal VoIP Daemon to a specific VLAN on the WAN interface. The Fritz!Box cannot just guest which VLAN to use, so it must be configured somewhere.

      Please make sure to distinguish between VoIP packets generated locally on the Fritz!Box and VoIP packets generated by devices connected to the Fritz!Box. The VoIP packets generated by the Fritz!Box is subject to the configuration element in the screenshot.

      The current behavior of the Fritz!Box is to route locally generated (inside the Fritz!Box itself) VoIP to the VLAN configured via the menu shown in the screenshot, all the remaining traffic, including VoIP traffic generated on devices connected to the Fritz!Box is routed via the VLAN 35 (the HighSpeed Internet VLAN).

      I will try to re-test the current situation in the upcoming weeks, unfortunately I have some other projects going on, so it may take a while.

  8. Hi again

    It works: I gave one of my Linksys’es to a colleague recently converted to luxfibre, proxy (SIP) and STUN already configured, IP through DHCP and he was able to ring me with that phone. Conclusion: you were right, fritz only sends to VLAN 39 only internally converted voice (analog/S0 port) or IP phones configured as such (obviously the requirement to connect directly the IP phone to a port means to let fritz ‘learn’ the MAC address).
    Pity that our german friends could not provide that information themselves after three weeks of persisting inquiries of mine, in both languages!
    After the installation I intend to run an FTP server.
    Anything out of the ordinary, I will gladly post to this nice blog.

    Good night

    • Thanks for saving me some work Antonis!

      (And yes you are right, if you configure an IP phone to use the Fritz!Box as SIP server/proxy/registrar then this SIP flow will again be sent to VLAN39. The SIP server on the Fritz!Box is a B2BUA (back to back user agent) so the SIP flow going towards the VLAN39 is not just routed as regular Internet traffic but as locally generated SIP traffic.)

      However, if supported by your LinkSys you can still configure the second SIP account/line on the Linksys to connect to the Fritz!Box that way you can make and receive calls via the primary non-EPT VoIP Account and receive calls for your EPT number via the secondary account (in case you want to use your EPT pone number on the Linksys).

  9. Hi,

    It works but you need to change the configuration manually in the file.
    Need to export your config (CFGFILE:ar7.cfg add NoChecks=yes to re import)
    And in the config of your 2nd provider change:
    route_always_over_internet = no;
    put route_always_over_internet = Yes;

    Info on:

    I can send you a print-screen with 2 registered phone numbers.

    Have fun…

  10. Hi, thanks for your blog, I switched to LuxFibre and have started experiencing problems with a VoIP SIP account that I use with a Siemens Gigaset S685IP base. The S685IP Base is registered on the FB7570 that EPT have given me to use LuxFibre. I found that immediately after having setup the SIP account I can use my Gigaset base to establish an external call or receive a call, but after 2 or 3 minutes any attempt to call generates an error message “Statut IP Code: 403” to start with and now “occupé”.
    I called the french provider OVH for help and stayed on their case for days. As I have another Internet connection via cable I tested the base on it: worked perfectly.
    I undertand now that the FB with EPT special config is probably the reason. I do not understand however how an Internet connection initially works (e.g. by un- and re-plugging the base to the mains) and then is dropped by the FB. Any idea?

    • There are usually 2 reasons for this issue.

      1) EPT doesn’t assign a public IP address to LuxFibre accounts by default. See . You will experience issues with VoIP and other protocols in such a situations. I have received 1 or 2 reports that EPT provides a public IP for free if you request one due to connectivity issues.
      2) You may need to activate STUN, NAT Traversal and Keep Alive functions on your Gigaset. In some cases it’s a good idea to set the SIP Registration Timer or Expiry value to 3 minutes or less. This will ensure that the “NAT hole” is kept open and SIP packets can flow between your Gigaset and your ITSP.

  11. To Keen doheem

    A disadvantage of the – working – configuration for two providers is that the box cannot anymore handle priorities at all: when moving large data (over 10 Mbyte) over the switch ports, all phone communications (bridged to EPT and routed to 2nd provider) are interrupted. AVM, as usual, refuses to help without returning the box to the original configuration.


    • The Fritz!Box is a powerful device, however the hardware is designed and priced to support the features officially offered to end users. I’m unaware of how the Fritz!Box may attach VoIP accounts to different upstream connection, but some ways I think of will require alot of CPU. OTOH you may have changed the switch configuration unnoticed so the switching is running via software and the CPU… I’m sorry I cannot help you here.

  12. Hello,

    I have been also amazed when I note that nothing was working like before with my FritzBox 7570.
    I found in your comments one solution about my problem of VPN, I will ask to the P&T tomorrow a public IP dynamic address, but for the voIP problem, I order another 5Mbits ADSL line to Orange.
    I have tried 3CX, v11 and their offert a lot of possibilities.
    Fritzbox is great because it’s an hardware solution, but It’s amazed all the functionnalities offert by 3CX with (possibility to link 2 offices, menu with deviations to the good service and a great soft on Iphone in order to select quickly my phone’s contacts (about 800). I was just amazed that XP was already not compatible, that’s the end of XP, really, hopefully that Win7 is stable now.

    Thanks for your help!

  13. Hello,

    I forget to tell that I tried to link my two FritzBox 7570, the second like simple client but only one of my voIP providers was recognized “linked” (only because calls was still not entering).
    Do you think that the problem come from the private IP address delivered by default with new fiber installation ?
    I could retry tomorrow if they provide me quickly my public IP address.
    If it’s the case, I will stop my second DSL in a year 😉
    Hopefully, Integral fiber is cheaper to compare at before.


    • You could try to configure a STUN server in the VoIP setting of the Fritz!Box. The VoIP daemon of the Fritz!Box connected to the LuxFibre line will only experience single NAT, anything behind the Fritz!Box will experience double NAT (including your 3CX). In case that works, you may register your 3CX via SIP to the Fritz!Box, that way you could get calls to work correctly (at least temporary if you don’t like the setup). The STUN server setting may only be available when connected via Fibre and not via VDSL.

  14. Hi, thanks for all this useful information. It helped to understand why the configuration of my second VOIP provider didn’t work out on my primary FritzBox.

    For those who are interested, I found a quite easy solution. My setup is this one:
    – primary FritzBox 7390 connected to the ONT
    – secondary FritzBox 7570 connected by LAN to the first one

    On the primary I’ve added a telephone device “SIP phone”, so using the secondary I was able to connect to it with an internet phone number (the settings are given by the 7390). All my devices are now connected to the second FritzBox (7570) and relayed via the first one.

    As the 7570 is connected to the internet, I was able to configure and use other VOIP providers. 🙂

    As the answering machine on the 7390 is quite better, I’ve just added a phonebook entry to the second one, pointing the internal number **700 to *#**600 which gives me access to the answering machine of the primary FritzBox using any device connected to the secondary one.

    • The latest firmware for the Fritz!Box 7390 allows to force a VoIP connection over the primary internet connection. So there is now an official workaround provided by AVM.

      • Great thing, thank you for your reply Marc, my colleague will be happy to read that, he was planning to order fiber in next weeks.

      • Hi

        I already did it in the very beginning (voipbuster over the internet link) using telnet. So now the optiion “Always register via an Internet connection” does exactly correspond to route_always_over_internet in the config. file, right?


        • I’m not an AVM developer, so I cannot tell you. You may want to analyse the configuration files for differences when activating the new option. I think to remember that you had QoS and load problems when activating this feature via telnet, I assume that AVM has optimised the involved software modules before making the option available in the GUI. So updating the firmware will probably give you more that just the GUI update.

          • Thanks
            I am on latest firmware since its release and I can confirm that my configuration was having no load problems, either before or after, in connection of course to that part (DECT problems were solved and NAS is anyway pointless – I purchased a Synology device, fair and square).

            So, after checking and comparing the two tel. numbers (P&T and voipbuster) I saw that where “Always register via an Internet connection” is set to yes (GUI), the flag route_always_over_internet is also set (conf. file).

            The only one problem I haven’t taken time to check is the interruptions in DECT traffic when some heavy file transfer occurs using WLAN. Let’s see.

            have a nice day

          • Ok, anyways, my colleague have to ask them another FriztBox because we have still older. We will update de firmware and will test. Otherwise, the two Fritz works fine.
            Thank you for your precision.

  15. Hi,
    thanks a lot for your blog as it saved me a lot of trouble back in 2011. Ever since i’ve worked with the old firmware and my own VOIP provider. Now, reading the blog again, i see your entry:

    2013/11/10 at 15:21
    The latest firmware for the Fritz!Box 7390 allows to force a VoIP connection over the primary internet connection. So there is now an official workaround provided by AVM.

    So can I do the firmware upgrade now without losing the privileges to use another VOIP provider?
    Thanks a lot for your help!

    • Hello Mark, that’s exactly what the option is for. I have used it successfully in Luxembourg on my LuxFibre 100 access.

  16. Ok, i will give it a try over the weekend. I only have the standard Junior account with the 7390, but I guess that doesn’t matter, as the old firmware forced you to only use the P&T services.
    Do you have a screenshot of the VOIP site? I use my VOIP account quite often and don’t want to lose that access. The wife would kill me, or actually her phone bills would. 😉
    Thanks a lot.

    • Ooops, just noticed that i actually have the 7570 VDSL! Ha ha ha, sorry! But i guess that won’t make a difference,right?

      • The 7570 VDSL is similar to the 7390 but not identical in all places. Concerning VoIP I don’t remember of any differences.

  17. HI everybody, and thanks for your helpful guides. Unfortunately , after days and days of unscucessful trials I am depressed. I recently moved from an appartament with ADSL to a house where we have fiber optiques, always with Tango.
    1 My Gigaset VOIP ( I have 2) do not work anymore ,
    2 Fritzbox 7390 provided by Tango ( OS 06.06) does not want to register the VOIP numbers ( “Always register via an Internet connection” checked) ,
    3 I also tried to use webservices based on PBX logic ( in order to use not standard ports ( as 80 , 5061, etc).
    4 I did the VOIP configuration also on a 7270 , but on the same subnet ( I may try to change the subnet) , no way
    I contacted Tango and I guess that the help desk has no clue about what I a am speaking.
    Any help around ?
    Thanks in advance
    Paolo Borghesi

    • Do you have TANGO TV? According to the latest information I have, if you have TANGO TV you’re sr**ed. AFAIK there is nothing further you can do, except to cancel your TANGO BLUE and reorder a new TANGO BLUE without IPTV or to order a Fibre Access with IPTV from another ISP. See here for further information

      • hi, I have not IPTV, I use sat tv based onmy beatiful linux based decoders

        • Well, in that case you might be able to solve the issue. If you want, please email me the VoIP log from your Fritz!Box and if possible the output of a traceroute to the server of your VoIP provider.

      • Hi and thanks a lot for the meaningful explanations. I can confirm of having Tango Blue , I will ask Tango about the IPTV.. I case I want to change provider, do you have suggestions ?

        • Paolo, I’m not sure why your Fritz!Box is unable to register with your ITSP. The only possibility that I suspect is a pre-configuration for IPTV that might cause an issue. In that case you may need to use this configuration workaround provided by AVM.

          • Hi Marc, I solved the problem through the use in cascade of a 2nd router on another net and the use of not standard ports, and a few small additional fine tunings. This is a configuration I initially tried several weeks ago and it didn’t work, therefore I did a full reset of the 2nd fritz and after the re-configuration the system started working. By the way, in EDPNET in Brussels, I had similar problems. Providers started to block ports and limit connectivity..

          • I’m glad it worked for you, cascading router and hence cascading NAT usually has the opposite effect. Eventually the factory reset did the trick… if you change to many things at once it’s difficult to tell.

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