To the knowledge base
Knowledge document #3339
FRITZ!Box 6660 Cable

Cable internet connection drops frequently

The internet connection between your FRITZ!Box and your cable provider drops frequently (several times a day). During this time, the Power/Cable LED on the FRITZ!Box flashes and then stays lit as soon as the internet connection is re-established. The following error message is displayed in the event log of the FRITZ!Box:

"Cable internet not responding (no synchronization)
Cable internet synchronization starting (training)"


  • The stability of the cable internet connection depends on the condition and the quality of the cable connection. Faults in the cabling or problems with the line can also affect it.

1 Checking the event log of the FRITZ!Box

  1. Click "System" in the FRITZ!Box user interface.
  2. Click "Event Log" in the "System" menu.
  3. Check whether events also took place before the time when the error occurred, or whether only events are shown that took place after the error occurred.
  4. If events are also displayed that took place before the time the error occurred, proceed with the next section.

2 Checking the cabling

Errors in the cabling often go unnoticed. Therefore, make sure that the FRITZ!Box is correctly connected to your line:

  1. Remove all cable extensions and adapters between the FRITZ!Box and the multimedia socket.
  2. Connect the coaxial cable included with delivery to the "Cable" socket on the FRITZ!Box and insert it into the socket labeled "Data" on the first multimedia socket. If a cable technician performed the original installation, use the coaxial cable provided by the technician to connect the FRITZ!Box with the multimedia socket used by the technician.

3 Contacting your provider

There may be a problem with the cable connection or the coaxial cable may be damaged:

  1. Contact your cable provider.