How to Test a DSL Modem

By Leighton Sawatzky

A faulty DSL modem can reduce your Internet connection speed.
i adsl image by Jean-Michel POUGET from

The maximum speed of your digital subscriber line (DSL) connection is limited by the speed of the package you ordered from your Internet service provider, but many home connections don't perform at that speed. This may be because your DSL modem isn't functioning properly. Perform an Internet connection speed test to see if your modem is working correctly

Close any programs using an Internet connection, such as file sharing programs.

Go to one of the Internet speed test sites linked in Resources 1 through 3.

Choose the location closest to you, if given a choice.

Click the "Start" or "Begin Testing" button. Your computer sends and receives files of pre-set sizes and the speed test tool rates your DSL connection based on how long the transfers took.

Go to the test linked in Resources 4 and 5 and click "Start." The ping test measures how long individual packets of data take to travel from your modem to the test website and back and how many packets are lost in transmission.

Disconnect the ethernet cable connecting your DSL modem and network router from the network router. Plug the other end into an ethernet port on your computer.

Repeat the speed and ping tests above. You should get the same speeds in both sets of tests if your DSL modem and network router are functioning properly.

Disconnect your DSL modem and set up another DSL modem in its place.

Run the speed tests again. The speeds recorded by the two DSL modems should be very close, if your modem is working correctly.