FritzBox 6890 LTE: great ambitions but bad results with serious Wi-Fi problems

A few months ago I was been able to update my home internet connection from an ADSL line to an FTTC line, so I also had to buy a new VDSL2 modem/router to replace the old ADSL2.

I would have liked to buy a VDSL2 modem/router on which to install OpenWrt and the only one available would have been the BT Home Hub 5 which unfortunately only supports profile FTTC 17a and not 35b, I could have bought a VDSL2 modem and connect it via WAN to an OpenWrt router but unfortunately the space available was little.

I then purchased a FritzBox 6890 LTE International v2 for the modest sum of 350 euros. The FritzBox 6890 LTE is a FritzBox 7590 with the added possibility of having a fallback network provided by an LTE SIM, which would have made me happy considering that I have several Linux servers accessible via the Internet.

The DSL modem part of the FritBox 6890 LTE is actually very good indeed it hooks up to the maximum carrier speed but this is the only positive note.

The telephone part works fairly well, but it is impossible to connect Android phones via VOIP, as can be verified from this discussion it is a problem that afflicts FritzBox devices for over 5 years and after some time has not yet been resolved.

The most serious problem of the FritzBox 6890 LTE (and almost certainly also of the FritzBox 7590) concerns the stability of Wi-Fi connections. If there are wireless devices always connected to the FritzBox, their communication speed collapses almost to zero in a completely random way, becoming unreachable but remaining connected with an excellent signal.

I noticed the problem because in my home I have for several years 4 Wi-Fi IP cameras of different brands (Bosesh and Vstarcam)  that connect via Wireless 2,4 GHz to the router and are managed by a Linux server with Zoneminder. The cameras have worked perfectly for years through a prehistoric Alice Gate 2 Plus Wi-Fi first and a cheap Asus DSL N55U_D1 then, but since I installed the very expensive FritzBox 6890 LTE the cameras started to become unreachable at random. Analyzing the situation I noticed that when a camera becomes unreachable in the event log of the Wi-Fi devices of the FritzBox there is no disconnection, in fact the camera is still present in the list of wireless devices connected to the router but its transfer speed passes from the excellent value of 150/150 Mbit/s at the painful value 7/1 Mbit/s, while maintaining an excellent signal. This happens randomly and unpredictably to one or more of the cameras, the problem may occur after a day or a week and each time the communication speed falls from 150/150 Mbit/s to 7/1 Mbit/s. When the problem occurs, the only way to allow the camera to be reachable is to turn off and on the Wireless connection of the FritzBox, in this way the camera immediately reconnects at the maximum speed of 150/150 Mbit/s.


To try to solve the problem I obviously tried all the possible combinations of the few settings that the FritzBox makes available, I tried to make the FritzBox manage the automatic selection of channels, I set different wireless channels all completely free and without disturbance, I have eliminated all possible interferences, I tried different stable and labor firmware (162.06.87, 162.07.03, 07.08-70570, 07.08 -70893, 162.07.12) but nothing to do, the problem persists. Among other things, both the cameras and the FritzBox are connected to a UPS and no USB device is connected to the FritzBox, so I was able to exclude any kind of power supply or power surge problem. I finally reinstalled the Asus DSL N55U_D1 and on it the cameras started working properly again.

After having tried everything to solve the problem and considering the impossibility of having more precise logs due to the impossibility of accessing the FritzBox through ssh, I then contacted customer support via email to indicate the problem, hoping that they would resolve it in a future firmware update, I provided a detailed description of the problem and all the attempts I made to solve it, I provided several screenshots and various assistance files. The customer support, however, appeared immediately arrogant and uncaring and, believing to speak to a fool, he first answered with stupid suggestions, then claimed the false hypothesis that the wireless channel used is disturbed, he finally concluded that the problem it's my IP cameras and that from the controls that they made my FritzBox 6890 LTE has no problem. Absurd!!!

Peeking the net I discovered that other users complain about Wi-Fi problems with the FritzBox 6890 LTE (here is an article in German) and complain about the bad AVM assistance.

I am more than convinced that what I described is a software problem that affects the FritzBox 7590 and the FritzBox6890 LTE. If you also have this type of problem, comment on this article or write to me in private, if we are many then we can force the FritzBox to consider it to solve it with a future firmware update.

Meanwhile, to date, given the previous problems, I have not tried either the connection with an LTE SIM or the DECT management. I do not know therefore what other surprises this device could reserve for me.

From my experience the FritzBox 6890 LTE is absolutely a modem/router not to buy.