ADSL Connection Troubleshooting

The display can be used for troubleshooting the ADSL connection. The dots in the display indicate:

. (one dot)
Power on, idle - no DSLAM has been detected. DSLAM

.. (two dots)
Power on, idle - DSLAM has been detected and ADSL training has been attempted to it.

(three dots)
DSLAM located and connection has been establised

To troubleshoot the ADSL connection:

  1. Turn on the Internet Gate and wait for a couple of minutes.
  2. Look at the display: One dot = no DSLAM has been detected, check and make sure that the ADSL modem is correctly connected. Two dots = a DSLAM has been detected but it cannot communicate with the ADSL modem. Three dots = a DSLAM has been detected and the modem has tried to establish a connection that has not succeeded yet.

The dots remain in the display until the unit is restarted. If there are two dots in the display you know that the modem has been in contact with a DSLAM since you turned the unit on.

If the modem has not been in contact with a DSLAM at all (one dot) you need to check the cable connected to the LINE port of the unit.

If the modem has been in contact with a DSLAM (two or three dots) but could not maintain a connection, or could not transmit data on the connection, then you need to check:

  1. VCI/VPI values on the Network page must match your Internet Provider's values.
  2. ADSL mode on the ADSL page must match the ones offered by the DSLAM at the other end of the connection
  3. ADSL standard on the Advanced ADSL page must match the one used by the DSLAM at the other end of the connection

Training, retraining and disconnecting

When the modem starts to negotiate, one rolling figure-of-eight is displayed on the frontpanel. From now on one can also follow the progress on the ADSL Status page, in the ADSL line state report.

If this first ADSL training step is successful, it is followed by a second figure-of-eight on the display, then a third, at which the ADSL link normally will be successfully established. By this time you should have a full frequency diagram on the ADSL Status page, the ADSL line state should be Active and the transmit and receive speeds (displayed on the ADSL Status page as well) should be as expected. You should also now get a “line: link up” message in the system log.

The display now shows one rolling figure-of-eight, accompanied by the text ”IP”, which indicates that the modem starts getting its IP address. This should not go on for very long, after some seconds (up to a minute) it should have got its IP address, and the display will shift to one of the steady texts Hi, Lo or AC. If this never seems to happen, see the internet access problems page for how to carry on the troubleshooting. It may be a problem with the VPI/VCI settings or some DHCP or PPPoE/PPPoA problems.

The ADSL connection, when successfully established, will stay up “forever” as long as the modem is powered on. However, disturbances can happen on the telephone line that may force the modem to drop the link and to retune to the apparently noisy line. In the ADSL language this is a retrain. This is visible on the display: the Hi, Lo or AC text disappears and is replaced by one or more dots (see above).
In the system log there is now a message

line(line): Link down.

accompanied by one or more lines telling, in technical terms, the causes of the link drop. For example:

ADSL: local loss of signal error
ADSL: local severely errored frames error

It is not always clear what causes such a disturbance. Surprisingly often, the fault is actually to be found at the customer's premises (i.e. inside your own building):

  • Is the ADSL connector and the splitter properly connected?
    :!: Generally, the ADSL modem should be connected to the 1:st (main) phone jack to get as clean signal as possible.
  • Are there more devices, apart from phones, attached to this telephone line, such as fax machines, answering machines etc? If so, try disconnecting them one at a time to see if the problem disappears.
  • Are there any disturbing appliances in the very close vicinity of the modem and its ADSL cable?

If no obvious source for the disturbance is to be found, and it happens frequently, the Internet (or ADSL line) provider's support should be consulted. The advanced user may consider to use the Force SNR Margin or even disable the Retrain parameter, see the ADSL settings page.

After a link drop the modem will constantly try to establish the connection again, without any user intervention:

  • If the dots remain on the front panel display, there is a constant disturbance or a broken cable connection that must be fixed.
  • If the retrain is successful and the link is established, the rolling figure-of-eight plus ”IP” reappears and the modem starts renewing its IP address again, as has been described above.
adsl/troubleshoot.txt · Last modified: 2010/11/26 14:00 by mats
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