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About DSL modem lights - TP-Link modems

The operational status of your TP-Link DSL modem is indicated by lights (LEDs). TP-Link modems have lights to indicate power, the status and activity of the DSL line, and the status and activity of connections to your computer, whether by ethernet or by wireless.

TP-Link modems have lights on the front (8901G) or the top (8816 and 8951).

Information is communicated by whether the lights are on, off or flashing. Activity on a line is often indicated by flickering lights, when the line is active.

Here's a summary of how to read the lights on TP-Link modems:

Contents

8816 Single Ethernet Port Modem

Power
Should be solid green. If it is unlit, there is a power problem or the unit is broken. Check that the modem is plugged in and switched on.
LAN (Local Area Network)
Should be solid green if a computer connected to the ethernet port.
ADSL (Asymmetric Digital Subscriber Line)
Flashes green when the modem is synchronizing, will be solid green once synchronization has occurred.
Internet
Will illuminate green when authentication has been successful, and will flash to show data traffic.


8901G 4-Ports + "G" Wireless Modem
8950ND 4-Ports + "N" Wireless Modem

Power
Should be solid green. If it is unlit, there is a power problem or the unit is broken. Check that the modem is plugged in and switched on.
ADSL (Asymmetric Digital Subscriber Line)
Flashes green when the modem is synchronizing, will be solid green once synchronization has occurred.
Internet
Will illuminate green when authentication has been successful, and will flash to show data traffic.
WLAN light (Wireless Local Area Network)
Will be solid green or flashing green if a computer is connected to the wireless.
Numbers
These lights correspond to Ethernet ports connected. These will show a solid green light when a computer is connected to the corresponding port by Ethernet cable.


8951ND Four Ethernet Ports, Plus "N" Wireless Modem

Power light
Should be solid green. If it is unlit, there is a power problem or the unit is broken. Check that the modem is plugged in and switched on.
ADSL (Asymmetric Digital Subscriber Line)
Flashes green when the modem is synchronizing, will be solid green once synchronization has occurred.
Internet
Will illuminate green when authentication has been successful, and will flash to show data traffic.
WLAN light (Wireless Local Area Network)
Will be solid green or flashing green if a computer is connected to the wireless.
WPS light (lock symbol)
Disregard
Ethernet lights
These lights correspond to ethernet ports connected. These will show a solid green light when a computer is connected to the corresponding port by ethernet cable.

Internet light

The internet light is steady green when the Central Office has accepted your modem's login and password and is ready to provide internet service via DSL to your modem. If the light remains unlit, there is a problem.

If your unit was able to log in earlier and you have not made any changes, an unlit light likely means that there is a temporary network problem (at the Central Office or NCF) making it temporarily impossible to check your login and password. In this case it is best to just wait for the problem to be fixed. You may need to power-cycle or restart your modem for it to notice that service has been restored. If you can get online elsewhere (by dial-up, at a friend's home or at an office or library), you can check the NCF web site to see if others are experiencing problems. If not, report the problem, although network-wide problems are almost always noticed quickly.

If you are installing your modem for the first time and the DSL light is green but the Internet light is unlit, likely your unit has not been configured with a correct login and password. Check the configuration instructions for information about configuring:

Beyond the lights

Lights can indicate only a small amount of information about your modem. To learn more about what your modem is doing, you can view your DSL usage log (this link is also available from the NCF StartPage, under 'Internet Access'). Often the pattern of connect/disconnects will reveal more information.

It is also possible to log into your modem (there is a computer with a Linux operating system in there) using a web browser, and then view its event log. For information about the modem's event log, consult the modem manual for your modem model.

Background information: Stages of DSL Connection-Making

This page explains how a DSL modem connects to the internet.

Start up

After powering up, a DSL modem typically goes through these stages:

  1. Self-testing
  2. DSL sync
  3. Authentication
  4. In-service

Self-test

Upon power-up, a modem typically performs tests to detect proper operation of its hardware and to detect problems in its software and data. This stage usually takes only a few seconds.

DSL sync

The first stage of connecting to the internet is to obtain a 'link level' DSL connection to the Central Office or DSLAM. Once established, the modem will use this connection to carry internet traffic.

Obtaining and maintaining a good DSL connection to the Central Office or DSLAM is crucial to good performance. To maximize performance, the modem tries to sense the quality of your phone line and adapt to conditions. The most basic requirement is obtaining DSL synchronization (detecting and locking onto the DSL signal).

Things that can go wrong at this stage, in order of most likely first, include:

  • no connection to the phone line
  • electrical noise from other devices on your phone line
  • low power signal caused by being far from the Central Office or DSLAM
  • electrical noise on the line from sources outside your location
  • problems at the Central Office or DSLAM.

Authentication

Once a DSL connection has been made with the Central Office or DSLAM, it can be used by the modem to talk with the NCF authentication server. This requires your modem to identify itself with a login and password (for security and billing purposes). Your modem can do the authentication for you but of course it must have been programmed with the correct information.

The most common problems at this stage include:

  • not having correct login and password information programmed into your modem
  • temporary network problems that prevent the authentication server from confirming the log-in information that your modem provides to it.

In-service

Finally, when the DSL connection is up, your modem has been authenticated and granted access, it tells your computer that it is ready. Your computer can then send and receive information from the internet. Requests go from your computer to your modem (via ethernet cable or wirelessly), then from your modem to the network (via your phone line), then over the network to whichever web site computer you specified.

Connecting to your modem

Your modem also looks for connections to your computer(s) via its ethernet ports or, if equipped and enabled, via wireless. The establishment of these links goes through similar stages as described above for DSL. Ethernet connections are usually quite reliable and trouble-free, but wireless connections can suffer from interference with other wireless signals. There are only eleven channels allocated for wireless use in Canada and in most urban locations, especially in apartment buildings or townhouse complexes, there can be twenty or more networks within range of your computer, which can make interference hard to avoid. For more information see About wireless.

Once you have a 'link level' connection to your modem, you can use a web browser to communicate with the computer inside the modem, just as if it were a web site on the internet.

See also