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Dokument informacyjny #1127

FRITZ!Box indicates numerous DSL connection errors

There is a problem with the DSL connection due to numerous errors on the FRITZ!Box's end or at your DSL internet service provider's exchange. As a result, internet access over the FRITZ!Box is very slow (when opening web pages or downloading files, for example) or problems occur when calling over the internet or playing back videos (for example IPTV or video on demand).


  • The data rate and stability of the DSL connection depend primarily on length and quality of the access line. Faults in the cabling or problems with the internet service provider's exchange (DSLAM) can also affect it.

Simply proceed as described below. After each measure, check whether the problem is solved.

Note:All instructions on configuration and settings given in this guide refer to the latest FRITZ!OS for the FRITZ!Box.

1 Checking the cabling

It is often difficult to recognize faults in the cabling and they can remain unnoticed for a long time. Therefore, check the wiring in your home:

  1. Remove the DSL splitter if you are using the FRITZ!Box on an IP-based connection.
  2. Remove all cable extensions, unused cables, telephone jacks, and additional electrical components (for example surge protection, automatic extension outlets).
  3. Make sure that the FRITZ!Box is correctly connected to your DSL line. For detailed information, refer to the quick guide included with the FRITZ!Box and the manual.

2 Installing the latest FRITZ!OS for the FRITZ!Box

Installing the latest FRITZ!OS makes your FRITZ!Box compatible with the latest DSL technology used by DSL providers in their DSL exchanges:

  1. Install the latest FRITZ!OS on the FRITZ!Box.

3 Increasing the interference resistance

Increase the interference resistance of your DSL connection; this reduces the number of errors due to brief disturbances on the DSL line:

Note:Increasing the interference resistance of the DSL connection may reduce the data rate of the DSL connection. However, the speed and quality of internet access may still increase because they are not affected by retransmissions.

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "DSL Information" in the "Internet" menu.
  3. Click on the "Interference Resistance" ("Line Settings") tab. If the tab is not displayed, enable the Advanced View first.
  4. Move one of the controls under "Receive Direction" one step farther to the left towards "maximum stability".

    Important:If the controls are moved too far towards "maximum stability", on some DSL lines a connection can no longer be established. Therefore, do not select the setting "maximum stability" right away. Instead, push the controls gradually to the left to determine the best setting for your line.

  5. Click "Apply" to save the settings.
  6. Click on the "DSL" tab.
  7. In the "Error Counter" section, check whether "Not Remediable Errors" (CRC) occur in the FRITZ!Box or the DSL exchange when the internet is used.
  8. If numerous errors continue to occur during the next 15 minutes, repeat steps 3 - 7 until no more errors occur.

4 Checking the DSL line

There may be a problem with the DSL line. Since it may take a while for your DSL provider to check your line, you may be charged for the service, and our experience shows that there is often a problem with DSL lines even if they have been checked by your provider, proceed as follows:

  1. Either: Check whether you also experience problems with your internet connection if you use a different DSL modem on your DSL line.
    • Or: Test whether you experience problems when you use the FRITZ!Box to access the internet on a different DSL line (for example at your neighbor's).
  2. If you also experience problems when you use a different DSL modem, or the FRITZ!Box can establish an error-free DSL connection on a different line, have your provider check your line.

    ATTENTION!You may be charged for checking. Ask your provider about charges in advance!