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How To Diagnose and Repair Basic Network Connection Problems

By Jason Imms

Practical tips for checking your connection and fixing a random disconnect.

Home networking equipment has reached a point of such ubiquity that it will soon be counted among common household appliances such as your TV, microwave and refrigerator. Unfortunately, it seems that the extent of most people's troubleshooting knowledge ends with rebooting their router and whining at the closest person they consider their personal tech support representative. This guide aims to provide a series of tools which can help you repair problems yourself, thus alleviating the pressure placed on those around you with any tech knowledge at all.

We've covered networking before, I won't be detailing tips for improving your Wi-Fi network, or configuring your router. Instead, let’s take a look at some common tools you can use in administrating your own home network.

A Doctor’s Tools

Ping (Windows command)

The ping tool, one of the simplest network troubleshooting tools available, is present in most common operating systems. It provides the ability to monitor attempts to transfer and return a network packet from one point in the network to another, thus proving that basic communication is possible.

Tracert (Windows command)

A command line tool which allows the user to trace the route taken by a packet from the source host to the target host. The IP address and hostname of each host are listed, along with the return time in milliseconds, allowing the user to find the source of delays in their network infrastructure, good sources for download mirrors and deciding which DNS server to use. A similar tool is available for Linux and MacOS and is known as traceroute.

ipconfig (Windows command)

A Windows tool which displays IP configuration information via the command line. A robust version of the network configuration options available via the Control Panel, ipconfig also allows for forced DHCP lease renewal via the /release and /renew switches. Some of the information display features of ipconfig are available on MacOS and Linux distrubutions using a tool called ifconfig.

iperf

Iperf is an open source, cross-platform tool which measures network throughput from one host to another, allowing the user to confirm that their network is transferring at the expected rate.

Angry IP Scanner

Angry IP Scanner is an open source application used for traversing a subnet and providing information on each of its active hosts. Helpful for finding unwanted devices on your network, confirming that your DHCP is performing as expected and finding the IP for a lost device. For more advanced purposes, nmap is available for most major operating systems.

Windows 7 Network Troubleshooting

Surprisingly enough, the troubleshooting tool provided with Windows 7 does an impressive job of automatically resolving common networking problems. It achieves this by performing tasks such as refreshing its lease with the DHCP server, resetting the network adaptor and confirming connection to its listed default gateway.

Confirming Basic Connectivity

All network troubleshooting is predicated on the assumption that your basic network connectivity is working as expected. The following are some simple checks that you can perform to confirm the presence of staple network connectivity.

Check Your Link Lights

On a cabled network, the simplest way to confirm a physical connection is to check that the link lights on the devices at each end of each cable are lit. If a light isn’t lit, check the plugs at each end to ensure that they’re securely pressed into the network sockets. Link lights are usually found on the network socket, or on the front of devices such as switches or LAN-capable routers.

Confirm Your IP Address

By default, your router will act as a DHCP (Dynamic Host Configuration Protocol) server. The advantage of using a DHCP server is that it will automatically manage the distribution of IP addresses to every device connected to your network. In Windows, check that your IP address is correctly configured by bringing up a command prompt (Windows Key+R, cmd, Enter) and typing ipconfig. Your router most likely defaults to providing addresses in either the 192.168.xxx.xxx, or 10.0.x.x ranges. If the IP address for your primary network adaptor is listed as something other than these ranges use ipconfig /release, then ipconfig /renew to renew your IP lease with the DHCP server.

Ping Internal and External Hosts

Using your Ping tool, attempt to confirm your connection to an internal host. Your router is a good option because if you can ping it, there is nothing between it and you that should be causing Internet connectivity issues. To do so, bring up a command prompt and enter ping [the IP address of your router]. By default, your router will most likely be found at 192.168.0.1, or 10.0.0.1. Having successfully pinged an internal host, attempt to ping a host external to your network using the command "ping google.com".

Confirm Standard Network Services

Having proven that a physical and logical connection exists for your network, it’s time to check the higher functioning services such as file sharing and media streaming. Attempt to copy a file from your current machine to another on the network. Use a small, but reasonably sized file for this to ensure that transfer rates are performing as expected. Next, attempt to stream media in much the same way. This time, use a large file like HD video to confirm that the network is able to maintain the transfer at a steady rate. Using iperf to confirm your network transfer rates is also suggested.

Loss of Internet Connectivity

The most common and arguably the most frustrating problem that faces users of any network is loss of access to the Internet. Right in the middle of an important IM conversation, gaming session or video stream, access can evaporate without warning or reason. There are a plethora of potential causes for this sort of outage, so the best approach is a systematic one. Check your local machine’s network connectivity. Is the operating system reporting that your machine is still connected to your local network? Check your physical cable or wireless connection to confirm whether or not local network access has been affected.

If you are still connected to your local network, the next step is to confirm connectivity to your router. Do this by attempting to navigate to its administration panel using a web browser. Simply type the IP address of the router into your address bar. Note that some brands of routers require the user to specify the network port for access to the admin panel. Do this by appending the necessary port number to the IP address in your address bar using a colon. Most routers that require a defined port will default to :8080.

Now that you’ve logged into your router’s admin panel, it is possible to determine whether external hosts are accessible from that point. Most good routers will have a ping tool built into the admin panel, often included in a diagnostics tab. If your router can successfully ping external hosts, while you cannot from your local machine the you can confirm that the problem exists within your network and can subsequently be fixed. As opposed to problems which exist outside of your network, and thus are out of your control.

If you’re unable to access external sources at all, it’s time for one last ditch effort--reboot your router. Even good quality routers can require a reboot from time to time, cheaper products, or those provided for free from some ISPs can require rebooting on a much more regular basis. This can solve a surprising number of problems from external connectivity problems, to spotty wireless performance.

Having failed all of these tests, it’s time to get your Internet Service Provider involved. Firstly you should check to see if they have any current advisories which are affecting your area and might be causing the problem. These are often listen on ISP websites, so use a 3G device or call a friend to get the info. Most ISPs will provide a time frame for these advisories which should give you a rough idea when it will be likely for your service to resume. If no advisories exist, call through to your ISP’s tech support and ask them for help. They’ll probably try to take you through a number of the steps listed above, but that’s ok. At least you’ll know what they’re asking you now!

Tips for Regular Network Maintenance

  • Keep at least one spare network cable around for testing or as a replacement.
  • Either repair or replace network cables with broken plug clips to reduce accidental disconnections.
  • Have a backup plan for infrastructure failure.
  • Don’t rely on a wireless connection for critical services.