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AVM provides workaround to use 3rd party ITSPs


The recent firmware update to Fritz!OS 06.00 allows to force VoIP connections to 3rd party ITSPs via the primary Internet connection.

FBforceInternet(Unfortunately I don’t have an english version yet.)

This new feature allows to use 3rd party ITSPs even if you have subscribed to IPTV or LuxFibre from POST Telecom or Visual Online.


  1. in french it is
    Authentification uniquement via une connexion Internet
    Si votre fournisseur d’accès à Internet réserve une connexion de téléphonie Internet à part à des numéros d’appel propres et si le numéro d’appel indiqué ci-dessus est celui d’un autre opérateur, activez cette option.
    (available in the FritzOS 5.52 of a retail Fritzbox 7390, not the Post homeserveur )

  2. Hello,

    Fantastic blog, thank you. Just a question, does this mean that any Fritzbox that haves the Fritz!os 6.0 can be connected directly to the Luxfibre ONT and we can get rid of there branded HW?
    I am asking as post is forcing me to move to Luxfibre, as my current Adsl is not working (it gives 96kbp) and post says that they do not repair it any more as everyone should move to Luxfibre.
    If I can use a retail FB I would go for it (I want my Voips to continue working), otherwise I would try to get another provider.

    Thank you for your reply,


    • Hello Andres,

      POST will probably provide a Fritz!Box 7390 which uses one VLAN for your Internet connection and another VLAN to provide your phone service via VoIP. That means that your analog and ISDN service is going to be migrated to VoIP unless you want to pay another extra. That also means that if you remove the Fritz!Box provided by POST or reset it’s configuration, you are going to loose your fixed telephony service!

      However this new feature allows you to use the Fritz!Box provided by POST to use any 3rd party service ITSP.

  3. Thank you Marc,

    I am new to Luxfibre, sorry for asking basic questions. You say that this new feature is part of Fritz Os 6, does this refer to the posts specific 7390? As far as I can see from avm and as mentioned above, this was already part of Fritz os 5.5 in the free FB. How would I get this feature on to the posts 7390?
    So if I understand it correctly, Posts fw follows the same naming (version 6) of fw but features are different?
    How often does post upgrade the fw of the 7390?
    I spoke with post support today, and they had told me that they plan to allow other voip providers on their 7390 in the future, but could not tell me when…. Are they just not aware of this latest feature?

    I am happy to share my knowledge on this blog,


    • I have seen 2 POST Fritz!Box 7390 where this new feature is available on version 5.5 or 5.52 (I don’t remember exactly). I have been using AVM Fritz!Box 7390 (no POST branding) with AVM Lab firmwares, so there might be a slight difference with OS numbering and features. If you have a version 5.5 where the feature is visible in the menu then you should be OK.

  4. Hello Marc,

    as said, I am new to this. I currently have a (non working) ADSL connection with a 7170. As they force me to migrate to Luxfibre, I am looking for the pitfalls and possible solutions. To recap, I see the following:
    1) It is possible to use an AVM 7390 (non Post branding) on an Luxfibre line. As seen in other forums, it will mean to fiddle around with the config file, but it is managable.
    2) If I do not want to do that, I am forced to take the post branded 7390. There I should have the option to use this new feature to use my other VoIp accounts

    As I do not like to be locked into capped fw versions, I will try to go for option one, hoping that it is not to difficult. I have friends that can give me their config files. Questions:

    1) Can you recomend a good link in which it is explained what things we have to configure to have a AVM (non post) 7390 running on the Luxfibre?
    2) Just in case, do you know what the differences between the post and the AVM firmware are? Is it major things?

    Thank you,



    • The essential thing about the LuxFibre service is the configuration of the Fritz!Box. If the Fritz!Box support the technical interfaces (VDSL or Ethernet) and the required configuration elements, you can use it even if doesn’t have the POST branding. I don’t encourage you to change the configuration files directly unless you know exactly what to do if anything goes wrong.

      POST uses 2 VLANs on VDSL and Fiber/Ethernet. VLAN 35 for Internet service and VLAN 39 for Telephony and IPTV service. The Internet service requires a traditional PPPoE session while the second connection uses DHCP, all of this can be setup via the web interface of the Fritz!Box.

      AFAIK POST uses the vanilla firmware delivered by AVM.

  5. Another question. Which one are you using, the international version or the German version? The international seems to be less advanced in terms of FW….

  6. Marc, as many here, I can’t get Fiber as of yet in our street in Luxembourg city (2015 maybe). However, I now saw that VO is offering 100/50 over VDSL in certain streets (not everywhere; try postcode 1913 and housenumber 38). It does mention “VDSL: additional equipment required” though. Is this really the case, can do they that over copper? On, it even “seems” as if they are offering 200/100 over VDSL (as I suppose Online doesn’t offer Fiber?).

    • By definition VDSL2 theoretically supports up to 100 Mb/s downstream and 100 Mb/s upstream. In practice you will probably see a throughput of something between 30 and 100 Mb/s, this really depends on the cable length from your modem to the VDSL DSLAM, the cable quality and other factors.
      I also don’t have technical details about the network of but it seems that they are providing fiber connections in certain locations.

  7. Thanks, Marc!
    100 down/50 up is a good alternative to the only other high speed connection we have available in our street, Numericable, with 120/5 (which I currently have). Ping times are bad with Numericable, around 30-40 ms when using within Luxembourg – so because of that and because of the much higher upload speed, I’m contemplating the 100/50 VDSL2 offer until fiber arrives. Do you think ping times with a VDSL2 connection can be lessened to 20 ms or less? Numericable’s network is net very well optimised, to say the least (everything goes through Brussels or Paris), as you can see below

    Tracing route to [] over a maximum of 30 hops:
    1 <1 ms <1 ms <1 ms
    2 * * * Request timed out.
    3 6 ms 6 ms 8 ms []
    4 23 ms 24 ms 23 ms
    5 23 ms 24 ms 25 ms []
    6 33 ms 33 ms 33 ms
    7 * * 24 ms
    8 * 23 ms 24 ms
    9 22 ms 23 ms 23 ms
    10 23 ms 23 ms 23 ms []
    11 24 ms 24 ms 23 ms []

    But of course, the question remains: is it worth the hassle to move everything for this. Download speed is actually very good with Numericable – I normally download at up to 120 Mbps without any problem during weekdays (down to 80-90 at weekends and some nights). But 5 Mbps up remains very poor.

    • Hi Fred, well the RTT values you’ve provided aren’t really bad. Of course the network path is longer and the RTT values is higher due to the excurse via the FranceIX. The downstream throughput sounds amazing, if you really don’t need the better upstream throughput than I would stay with the current setup as VDSL may deliver less throughput. A throughput of 100Mb/s is only possible on lines than run less than 500 meters.

      At you address you could be connected to 2 different paths via POST, both under 500m. So you should be able to get VDSL100 with some decent speed. If you can afford/accept to have a somewhat lower throughput on your download and get a better upstream throughput, than you may want to go that way. As always I cannot give any guarantee whatsoever. Ask your ISP about the availability before subscribing.

  8. Thank you for this info 🙂

    I have aFritz!Box 7390 with firmware 5.52 and have verified that the option authentication within internet is available, so now what voip provider could I use for instance ? I’m currently using of course and I’m quite happy with it.

    • You can use any ITSP supporting SIP (in theory, in rare cases an ITSP limits it’s offer to their country or region only).

  9. Marc, you seem to have access to a lot of information. Can you check for post code XXXX and house number YY what the distance is?
    For me upstream is quite important, so that’s why I am considering moving. And it seems Numericable won’t invest in their network at all, and anyways, it seem cable providers’ upstream is always a lot less than downstream. More than 10 Mbps on cable for private customers seems impossible – probably due to the technology they use. Even in surrounding countries, I did not find any cable provider with more than 10 Mbps upstream; most only give 3 to 6 Mbps.

    • It should be possible to get VDSL100 installed at your location with quite decent speed, a path with less than 500m is eventually available. Fibre is planned for end of august 2015. Again NO guarantees at all. The situation at your location might differ from what has been documented or may differ to you specific conditions at your location. Ask your ISP about the availability before subscribing.

  10. Thanks Marc. VO will do the install in a few weeks. DSLAM distance is 353 meters. So I hope I’ll get full throughput on a 7490. And that, as an added bonus, I’ll finally be able to part from Numericable, who, by the way, still give Belgian IP addresses to every single Luxembourg subscriber 😉

  11. Well, in the end, POST can’t offer 100 Mbps bonding on my address at all. Something to do with “endpoints” and different routes, and as a result of these two routes/lines necessary the distance is too much. So I had to cancel. Damn 🙁

  12. This is it: “La tête terminale n’a pas assez de paires pour connecter 2 lignes en tant que bonding OU Les 2 paires de cuivre possible à cette adresse sont sur 2 têtes terminaux différentes, qui ne peuvent pas être raccordés ensemble.” I’ll try to get more details and see if they can’t change something there… What do you think, Marc?

    • Fred, the described situation is possible, sometimes the physical network setup differs from the documented setup. Did you get this reply for a VDSL100 or VDSL30 installation?

      • It seems they have now modified something and will try the installation again in January. This was for VDSL100 bonding. VDSL30 works just fine (maximum speeds).

  13. Hi Marc,

    Got my Luxfiber today. As you mention, so far everything is working fine. Thank you for all the good ideas.

  14. Hi,
    Great thread! I just took delivery of a VDSL100. My problem is that without telling me they disabled my other line which I used for fax and the security system..
    Basically what was done is that two telephone lines where merged into one new router from Sagemcom. The Fritzbox (7390) still has to be used for the VOIP. In my opinion, it’s a bit of a messy installation compared to previous…
    Speedtest gives me 91.96 Mb/s 49.93 Mb/s 20 ms

    • Hello Ben, if your previous installation with 1 single ISDN line with one or more MSN, than the described procedure is the default procedure. During a migration from ISDN with MSN to VDSL, you usually get 1 VoIP Account for each number (ISDN & MSN) you had previously. With VDSL you usually have the possibility to receive your telephony service via analog or ISDN line, at an additional cost. I don’t know how reliable fax works via the VoIP service from POST Telecom. The security service should work just fine over VoIP, unless it tries to transmit data using an integrated modem, DTMF should work fine.

  15. Hi Marc; many thanks for your feedback.
    We had Luxfiber30 before; and got the Fritzbox 7390 with that. A regular POTS phone worked with the Fritzbox but the security system did not for some strange reason. Brinks confirmed this. So fax and security was on a pure analog line. Then comes Luxfiber100 and takes that line !! Anyway, the analog number was changed to a voip and put on the second output in the 7390 and FAX seems to work fine like this. I have to change the security system to a GSM solution (cost 600€..).
    To be honest; I don’t recommend this setup. Fiber will come April next year and I should have waited for that…

    • Your VDSL100 probably uses bonding of 2 copper pairs, which made it necessary to use your POTS copper pair for VDSL100. It seems that your security system is transmitting service states to Brinks via a dial-up data connection. I’m puzzled why people still use such antiquated techniques in times where most everything is IP based. Mobile networks will switch to IP based transmission for voice (and dial-up modems) once Voice-over-LTE is released. But dial-up modems are probably just like IPv4 😀

  16. Exactly. Both copper lines were taken (would have nice to know before!).
    2 small black boxes are put on the outtakes and are connected via a Y-cable to a modem.
    Brinks offered me both GSM or IP now. GSM was 100€ more but I guess it’s more “secure”.

    • I’m not sure what you mean by

      more “secure”

      . Today most cables are buried, making physical access to them quite difficult, OTOH pocket mobile phone jammers are sold on every corner. All depends however what you’re trying to protect your home against, this will determinate the vectors against which you may want to protect your security system.

  17. Thanks. I’ve upgraded to 6.01 international version now. Samba for the USB NAS doesn’t work anymore due to this release :-/

    I’ll try to find an ITSP with Google

    • If you could define “doesn’t work” more specifically, someone might be able to help.

      • Hi Marc,

        I’ve upgraded to 6.03 since.

        By “doesn’t work” I meant they’ev removed the functionnality, no more SMB share anymore currently but they told me it will be back with no date.

        Anyway, since I’ve upgraded to 6.xx firmware my VDSL30 line is slower than before.

        I had :

        Informations DSL
        Débit de données
        32632 kbit/s (à la réception) 11152 kbit/s (à l’envoi)
        Affaiblissement de
        20 dB (à la réception) 102 dB (à l’envoi)
        Rapport signal/bruit 11 dB ((à la réception) 11 dB (à l’envoi)
        Version DSL
        État DSL actif depuis 06:11:25:27
        Multiplexeur d’accès

        with 6.01 I had :

        Informations DSL
        Débit de données
        28344 kbit/s (à la réception) 11152 kbit/s (à l’envoi)
        Affaiblissement de
        20 dB (à la réception) 102 dB (à l’envoi)
        Rapport signal/bruit 16 dB ((à la réception) 11 dB (à l’envoi)
        Version DSL
        État DSL actif depuis 02:14:58:32
        Multiplexeur d’accès
        Ikanos 0.1

        and now with 6.03 I have :

        Informations DSL
        Débit de données
        24048 kbit/s (à la réception) 11152 kbit/s (à l’envoi)
        Affaiblissement de
        20 dB (à la réception) 102 dB (à l’envoi)
        Rapport signal/bruit 19 dB ((à la réception) 11 dB (à l’envoi)
        Version DSL
        État DSL actif depuis 04:22:15:32
        Multiplexeur d’accès
        Ikanos 0.1

        AVM support asked me to downgrade to 5.x to take a trace and send them back with 6.x dsl trace but I do not want to lose parameters and (call) history of my fritzbox.

        Do you have an idea about what happened ?

        I noticed the DSL version is higher and the signal/noise rate changed, anyway the bandwith is lower than before :'(

        • Hello 🙂

          Contacted and they found I had issue on my line since the firmware upgrade … whatever, they’ve done something rebooted the fristbox and now everything is perfectly fine !!!

  18. Hi Marc, do you know if the Fritzbox 7390 international version (e.g Austria/Switzerland or any other version) will work in Germany?
    After many hours of search on the official sites, forums etc. I found no answer to this simple question. I would like to buy this router to use it in Germany, but the interface must be in English. It has been difficult to find out any information.

    There is a lot of talk about how possible or impossible it is to change the German version to use an international firmware,but that is not what I want. From what I can see, the international version seems to support the same standards the VDSL connection here has, including Annex A or B. But there is nowhere a clear statement about whether the thing would work normally or it would but missing something or it simply would explode in flames. If so, it would be interesting to know why it would not work or why it would explode… 🙂

    My internet package is for telephone and internet only, not for TV.


    • The international Version support Annex A and Annex B for ADSL, and the german version (used to) support Annex B only. AFAIK you may not load a German firmware onto an international Fritz!Box as the hardware differs. The firmware doesn’t affect the hardware capabilities. I would suggest contacted the AVM support, providing the exact model number of your Fritz!Box and the ISP and service you want to use in Germany. The AVM support should be able to answer your question. I have made the experience that the AVM support is very knowledgable so it’s worth giving it a try.

  19. Marc, I’d like to get your opinion on using different DNS servers. I am having strange results. I’m with VO, and when for example I do a traceroute to, I get this result:


    Tracing route to [] over a maximum of 30 hops:

    1 <1 ms <1 ms <1 ms []
    2 23 ms 23 ms 22 ms
    3 22 ms 23 ms 22 ms
    4 25 ms 23 ms 23 ms []
    5 23 ms 24 ms 23 ms []

    When, however, I change my DNS servers to Google's, I get this, using the same connection:


    Tracing route to [] over a maximum of 30 hops:

    1 <1 ms <1 ms <1 ms
    2 22 ms 23 ms 23 ms
    3 22 ms 23 ms 22 ms
    4 * * * Request timed out.
    5 * * * Request timed out.
    6 27 ms 27 ms 27 ms []
    7 27 ms 27 ms 27 ms

    The odd thing is, the page ( also loads excruciatingly slow using Google's DNS servers. Now I don't understand this, I though all DNS did was translating hostnames to IPs. Routing shouldn't be affected, should it? What's your take on this? The only thing I can think of, is that this site uses Akamai, and somehow attributes a different IP address to requests from Google's DNS servers, as seen above. Even then, I would think Akamai can handle this.

    • The DNS answers may be generated in the fly by the authoritative DNS server and as such no 2 queries may receive the same answer. This topics is however much much to broad to explain in a short comment. I will probably publish some articles in the future about DNS assisted load-balancing, geo-distribution a.s.o.

      Concerning your initial question, I think it is important, these days, to understand who will be able to analyze your DNS requests. Other factors might be the time required for the DNS answers to arrive and the general availability of the DNS service. As you have noticed, some sites may provide different performance depending on which DNS resolvers are used, but the number of sites affected by this is probably very small.

  20. Pingback: LuxFibre disables alternative VoIP services? - Marc's Blog

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