FRITZ!Box 3390 Service - Knowledge Base
FRITZ!Box indicates numerous DSL connection errors
You are experiencing problems with your 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 you open web pages or download files, for example) or problems occur when you conduct internet calls or play back videos (for example IPTV or video on demand).
- The throughput and stability of the DSL connection primarily depend 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.
Note:All instructions on configuration and settings given in this guide refer to the latest FRITZ!OS for the FRITZ!Box.
Simply proceed as described below. After each measure, check whether the problem persists.
1 Checking the cabling
It is often difficult to recognize mistakes in the cabling and they can remain unnoticed for a long time. Therefore, check the wiring in your home:
- Remove the DSL splitter if you are using the FRITZ!Box on an IP-based connection.
- Remove all cable extensions, unused cables, telephone jacks, and additional electrical components (for example surge protection, automatic extension outlets).
- Make sure that the FRITZ!Box is correctly connected to your DSL line. You will find detailed instructions on the installation poster included with the FRITZ!Box and in 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:
- 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 can reduce the throughput of the DSL connection. However, this can increase the speed and quality of internet access, as they are not affected by retransmissions.
- Click "Internet" in the FRITZ!Box user interface.
- Click "DSL Information" in the "Internet" menu.
- Click on the "Line Settings" tab. If the tab is not displayed, enable the Advanced View first.
- Move one of the controls under "Receive direction" one step farther to the left towards "Maximum Stability".
Important:If you move the controls too far towards "Maximum stability", with some DSL lines you will no longer be able to establish a DSL connection. 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.
- Click "Apply" to save the settings.
- Click on the "DSL" tab.
- Check in the "Error Counter" section whether "Not Remediable Errors" (CRC) occur in the FRITZ!Box or the DSL exchange when you use the internet.
- If numerous errors still occurred during the last 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:
- 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).
- 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!