All of the computers in my household are connected to a router either via Ethernet cable or wireless. The router is connected to a broadband modem which provides internet access to the home network. This has been working fine for the past few months, but recently has been unreliable with internet access lasting about 15 seconds and then a message will appear informing that there is limited network connectivity and the internet will not work for about 60 seconds, at which point it returns for 15 seconds and the cycle continues. I have contacted my ISP and confirmed that nothing is wrong with the internet connection itself and suggested that I contact the vendor of the router and modem. The modem vendor suggested that the problem must be with the router as the internet connection is stable and works correctly when the modem is directly connected to the computer. Do you agree with this diagnosis, and is there anything I can do to fix the problem?

From your description of the problem it does certainly seem to be related to the router. As the internet is stable when the broadband modem is directly connected to the computer, this indicates that the problem must lie between the modem and the computer. The only intermediate steps between the modem and computer is the router and cables connecting the router to the modem and router to the computers (which are connected via cabled Ethernet). I assume that the same problem occurs with computers connected to the router via wireless, so we can discount the cables connecting the computers to the router as the culprit. Therefore, this just leaves the cable connecting the router to the modem as a potential culprit. However, the message which is appearing on the computers about limited connectivity is likely the well-known Windows “Limited or no connectivity” message. This indicates that the computer is not able to obtain an IP address or cannot router any network traffic to destinations. This explains the reason why the internet stops working, as your computer is essentially falling off the network entirely. This is a problem with the router itself, as it is not correctly handling network traffic. As such, we have determined that the problem is now with the router itself.

As we have confirmed the problem is the router we need to troubleshoot to see whether there is anything we can do to resolve the problem. In the first instance, you should perform a factory reset to bring the router back to the factory default settings. This will eliminate any potential configuration problems as the cause, allowing you to setup the router from scratch. Before doing this ensure that you have all the relevant details for your ISP handy (such as the username and password for your account, together with any other required configuration information) as this will need to be re-entered into the router during the setup. The exact procedure for completing a factory default reset differs between routers, so I cannot provide specific instructions as I do not know what kind of router you are using. However, you should be able to find instructions for this procedure in the router manual (which should also be downloadable from the router manufacturer’s website, if you don’t have the original manual handy).

If the problem continues after completing the factory default and re-setup of the router, you should next check whether there is any updated firmware for the router. Firmware is the software which runs on the router. If there is a bug in the firmware it could be causing this problem, and an updated version of the router firmware may fix the problem. There should be a facility within the router administration page to check for updated firmware or you can alternatively check the manufacturer’s website for firmware. Make sure that you follow the exact instructions for updating the firmware, and only install firmware which is designed for your router, as incorrectly updating the firmware could result in your router becoming unusable. So only proceed if you are confident in completing the update process.

Should the problem continue, it seems that the router itself has developed a fault. In this situation I would recommend purchasing a new router. As you may have read in a column a few weeks ago, routers do quite a tough job as they are running 24 hours a day 7 days a week without rest so it is not a complete surprise when a router that has provided many years of faithful service starts to develop a fault. In fact, this could be a good opportunity to purchase a router and modem combination unit, so that you don’t need to have two separate devices. Just make sure that you purchase the correct type of unit. In particular, if you have an ADSL internet connection then you will need a different kind of modem/router unit compared with if you have a cable internet connection. You should check with a knowledgeable person in the store that you are purchasing the correct type of modem/router for your internet connection as all the different types can be quite confusing.