Troubleshooting ADSL or Naked DSL Speed Issues

This article will show you how to troubleshoot speed issues for ADSL1, ADSL2+ or Naked DSL.

Select one of the links below to jump to a query:

  • Speed test run on an Ethernet cable-connected computer shows speed slower than 1.5Mbps (1500kbps)
  • Connection speed much slower than it used to be
  • Files take a long time to download despite being small in size
  • All websites don’t load properly or suffer lag


Potential cause Try this:
Call dropouts or line noise on your Home Phone Always troubleshoot phone dropouts or line noise issues before focusing on any internet issues. Slow speeds may just be a side effect from a phone line problem.
Weak WiFi signal Test your speed on a computer connected to your modem with an Ethernet cable.
Virus or malware infection Run an antivirus/anti-malware scan using your antivirus software. Please contact your security software’s Customer Support if you need a hand with this.
Firewalls or other antivirus software negatively affecting internet performance Test your speed while firewall/antivirus software is temporarily disabled. Please contact your security software’s Customer Support if you need a hand with this.
Data congestion Disconnect any additional devices from your home network.
Network congestion Test your speed at multiple times of the day, particularly if speed only slows around in the evening, when network traffic is usually the highest.
Modem settings or connection stability affecting speeds Try putting your modem settings into "safe mode" (G.DMT mode). Guide for iiNet modems. This is particularly useful if you have ADSL1 or if you are a long distance from the telephone exchange.

If you have a third-party modem, please consult its user manual or contact the manufacturer for information on how to put it into safe mode.


Note for Naked DSL: Please skip to step 4, as you don't have a landline phone service to troubleshoot.

  1. Unplug all devices from every phone socket, including modems, telephones, fax machines, other modems, pay TV boxes and EFTPOS terminals.
  2. Plug a standard telephone handset (with no filter) into the phone socket. Listen for a dial tone and make sure you can make a call without hearing noise or interference. If you do hear noise, switch to line noise troubleshooting.
  3. If you have no phone issues, unplug the telephone handset and instead plug your modem directly into the phone socket (with no line filter).
  4. Connect one computer to your modem with an Ethernet cable. If you have any other computers cable-connected to your modem, unplug their Ethernet cables.
  5. Turn off or disconnect any computers or devices connected to your WiFi network. Alternatively, some modem/routers may have a WiFi on/off switch you can use to temporarily disable your WiFi network.
  6. Run a speed test. If your speeds are faster now, follow the advice below.
  7. If your speeds are still slow, if possible, try using different phone cable to plug your modem into the phone socket, and a different Ethernet cable to plug your computer into your modem.
  8. Run another speed test. If your speeds are faster now, follow the advice below.
  9. If possible, plug in a different modem (with no filter) into your wall socket and run another speed test. If a different modem gives you improved speeds, the first modem may be faulty and may need to be replaced.

    If a different modem also gives you slow speeds, then it's safe to say that the original modem isn't faulty.

  10. If your speed issues persist, please call us on 13 22 58 for further assistance.


  1. If your speeds go back to normal when you have just one computer connected to your modem, you can start plugging your other equipment back in, piece by piece. Start with any phones or faxes and their line filters.
  2. Wait a minute or two after each device is plugged back in, and then run another speed test.
  3. If your speed suddenly drops, the cable or device you’ve just plugged in is probably affecting your speeds. It may be faulty, or if it's a phone and/or fax device it may just need to be plugged into a line filter before being plugged into the wall.
  4. If your device already has a line filter, it may be the filter that is faulty and needs replacing. If possible, try plugging it in with a different filter and check if your speeds improve.


Why do I need to test a different modem?

Speed issues can be caused by several things, but two of the most common causes are problems with a modem or damage to your copper phone line. Your speed conditions are unique to your address, so modem testing must be done at your property.

If iiNet lodges a fault for a service when there is no fault (e.g. caused by a fault modem) then you may be charged an incorrect call-out fee by our wholesaler’s fault technician. While we understand that not every may be able to test another modem, we strongly recommend it wherever possible because it's the best way to reduce the risk of incurring an incorrect callout fee.

This and other troubleshooting helps to rule out as many other possible causes for your connection issue as we can.