FRITZ!Box 3390 Service - Knowledge Base
DSL connection drops frequently
The DSL connection between the FRITZ!Box and your DSL provider's exchange drops several times a day. When this occurs, the "Power" LED on the FRITZ!Box flashes and stays lit as soon as the internet connection has been reestablished.
If you have a DSL line with an additional analog landline, this problem may occur very often when you accept a call to your landline number or make a call from your landline.
The following error message is displayed in the event log of the FRITZ!Box:
"DSL not responding (no DSL synchronization)
DSL synchronization starting (training)"
- The stability of the DSL connection primarily depends on the 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 persists.
Note:All instructions on configuration and settings given in this guide refer to the latest FRITZ!OS for the FRITZ!Box.
1 Checking the event log of the FRITZ!Box
- Click "System" in the FRITZ!Box user interface.
- Click "Event Log" in the "System" menu.
- Check whether there are any events that occurred before the error did, or whether only events that occurred after the error are shown.
- If events that took place before the error occurred are also shown, continue with the next section:
- If only events that took place after the error are shown, follow the instructions in our guide FRITZ!Box restarts occasionally.
2 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.
3 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.
4 Increasing the interference resistance
Increase the interference resistance of your DSL connection; this reduces the number of interruptions of the DSL connection due to brief disturbances on the DSL line:
Note:Increasing the interference resistance of the DSL connection can slightly reduce the throughput of the DSL connection.
- Click "Internet" in the FRITZ!Box user interface.
- Click "DSL Information" in the "Internet" menu.
- Click on the "Interference Resistance" ("Line Settings") tab. If the tab is not displayed, enable the Advanced View first.
- Next to "Intended signal-to-noise ratio" under "Receive direction", move the setting 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 may no longer be able to establish a DSL connection. Therefore, do not select the setting "Maximum stability" right away. Instead, push the control gradually to the left to determine the best setting for your DSL line.
- Click "Apply" to save the settings.
- If the DSL connection continues to drop frequently, repeat steps 4 - 6 until the DSL connection is stable.
5 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:
- Disconnect the FRITZ!Box from the DSL line.
- Connect a different DSL modem to the DSL line.
- Test whether the DSL connection remains stable when you use this DSL modem.
- If the connection continues to drop, have your provider check your line. There is a problem with the DSL line.
ATTENTION!You may be charged for checking. Ask your provider about charges in advance!