Diagnosing an Internet Outage

When a computer loses its connection to the Internet, Internet Explorer will fail to display the home page and will display a text message instead:

“Internet Explorer cannot display the webpage”

Displaying a web-page requires a lot of individual elements to perform successfully, including:

1. The station must have a valid and current IP address, either provided dynamically by a router or server that provides DHCP, or a non-conflicting static IP address. The Windows IPconfig command can be used to confirm that a station has a valid IP address.

2. The station must be able to send and receive a DNS lookup request to a valid and working DNS server. The DNS server converts the requested name into IP address of the web-site. The Windows NSlookup command can be used to test the availability of a DNS server.

3. Port 80 for web pages must not be blocked by firewall software or diverted by a virus.

There are many different causes for Internet failure, but a few simple tools and tests can be used to quickly locate the problem. Typical causes, symptoms and solutions for Internet failure include:

  • Internet provider service outage: all stations lose Internet at the same time. Cable or DSL modem lights will show connection failure. Notify the service provider.
  • Router lockup; power off and restart router.
  • Ethernet switch failure due to overheating, lockup or power failure. Power off and restart.
  • Workstation cabling problem; remove and re-insert cable, replace any damaged cables. 99% of all cabling problems exist at the ends of the cable and are due to wiring failure inside the end connectors.
  • Server problem, although most servers do not control the Internet connection, unless the server was configured to provide DHCP (dynamic IP addresses) or DNS. Rather than restart a server, the DNS and DHCP software can be quickly and easily restarted using the NET STOP and NET START service commands.
  • To improve the reliability of a network, we recommend configuring the router for DHCP and then making the server the primary DNS with a secondary external DNS server. This ensures that if the server is unavailable, stations will continue to receive an IP address and reach the Internet. Rather than use the DNS servers provided by the Internet provider, we recommend using Google’s DNS servers at 8.8.8.8 and 8.8.4.4.

    The two best tools for troubleshooting an Internet connection failure on a station are IPconfig and NSlookup. To use either tool, select the Windows start button, choose the Run option and type: CMD at the Open prompt. This will display a command prompt where IPconfig and NSlookup can be used to check the status of an Internet connection. Typing EXIT when finished will close the window and return to Windows.

    When both IPconfig and NSlookup work properly but Internet Explorer fails to display a web page, this is typically an indication that the Internet Explorer settings have been modified by a virus or malware program.

    There are many tools available to check the files and settings in Internet Explorer. Successfully recovering from a virus requires removing the virus and then repairing the damaged and modified settings in Internet Explorer.

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