How To Diagnose Internet Connectivity Problems

Network connectivity problems can be the result of a variety of issues. This article goes through potential issues that could cause connectivity problems, including DHCP settings, proxy settings, and device drivers.

Question

How can I diagnose my Internet-connectivity problems?

Solution

Diagnosing a failing Internet connection can be fairly complicated. There are a number of different factors involved in the chain between the software configuration, the firmware drivers, the hardware device, the network equipment, and finally the Internet service provider (ISP) uplink. If any one link in the chain is broken, the connection won't work. However all the user may experience is a web page won't load. In other words, it's not always immediately clear specifically which part is failing.

This page will cover just about everything that could possibly go wrong and is organized by the order in which you should verify things.

Contents

1. DHCP Settings
2. DNS Settings
3. Proxy Settings
4. Third-party Firewall
5. Malware
6. Network Equipment
7. Device Drivers
8. Hardware

DHCP Settings

Verify that you have a proper IP address from the DHCP server

Check that can help narrow the problem down is checking the assigned IP address.

1. First you will want to know the nature of the network you're connecting to, e.g., from home or the university and wired or wireless connection.
   1. Common local network IP addresses, such as for personal switches and wireless routers, begin with 192.168.1... or 192.168.0...
   2. On the university network, wired IP addresses typically begin with 128.223... and on the wireless network, 10.112...
2. We will want to check our IP address to see if it is in the proper format.
   1. If the IP address looks incorrect (commonly if this is the case it will default to a 169.256.... address) we need to fix the DHCP settings.
   2. In this case, a manual address has been entered and the configuration needs to be changed back to using DHCP.

Windows

• Go to Start > Run > type in cmd
• A Command Prompt window will appear. Type ipconfig. Scroll down to  IPv4 Address will be listed your IP address.
  • If the format looks correct, continue to the next section
  • If it looks wrong, such as a 169.256... address or a 0.0... address, we need to check the DHCP settings.
• Open up Control Panel and go to Network and Internet. 
  • Open the Network and Sharing Center, then select Change Adapter Settings. 
  • Right-click the primary connection you are using, be it Ethernet or wireless, and go to Properties.
  • Locate the TCP/IP protocol and double-click it.
  • Make sure the first setting is set to Obtain an IP address automatically and then re-test the connection.

If it is still grabbing an IP address starting with 0.0... or 169.256..., the problem is most likely driver/hardware related.

macOS

• Open up System Preferences and go to Network.
• Click on the connection you are using.
  • On the main panel there it should say the IP address assigned to it.
    • If the format looks correct, continue to the next section
    • If it looks wrong, such as a 169.256... address or a 0.0... address, we need to check the DHCP settings.
• Click Advanced, go to the TCP/IP tab, and make sure it is set to using DHCP. Re-test the connection.

If it is still grabbing an IP address starting with 0.0... or 169.256..., the problem is most likely hardware related.

DNS Settings

Verify that the DNS server is functioning

The connection may be working entirely but there could be a problem with the domain name server (DNS). DNSs are responsible for translating an alphanumeric name, such as www.uoregon.edu, into a physical IP address, such as 128.223.1.1.

We can do a simple test by pinging a static IP address. I like to ping 4.2.2.2 because it's an easy address to remember. If the ping is unsuccessful then there is a deeper problem with the connection and you should continue on to the next section. If the ping is successful than the DNS server settings should be verified.

Windows

Go to Start > Run > type in cmd.

• Type ping 4.2.2.1.
  • If you don't get a reply, there is a deeper issue with the connection, continue on to the next section.
  • If you do get a reply but do not get a reply to a name address such as www.google.com, then we need to check the DNS server settings.
• Open up Control Panel and go to Network and Internet. 
• Open the Network and Sharing Center, then select Change Adapter Settings. 
• Right-click the primary connection you are using, be it Ethernet or wireless, and go to Properties.
• Locate the TCP/IP protocol and double-click it. On the page that comes up is the DNS info.
  • If the DNS server is not set to automatic, set it to automatic and try that.
  • If it's still not working, there are a couple of manual DNS entries that you can use.
    • 4.2.2.1 or 4.2.2.2 is a public DNS server.
    • There is also OpenDNS: 208.67.222.222 or 208.67.220.220

If manual configuration isn't working either, continue to the next section. 

macOS

• Go to Applications, go to Utilities, and open Terminal.app
• Type ping 4.2.2.1 
  • If you don't get a reply, there is a deeper issue with the connection, so continue on to the next section.
  • If you do get a reply but do not get a reply to a name address such as www.google.com, then we need to check the DNS server settings.
• Open up System Preferences and go to Network. Click the connection you are using, Ethernet or wireless, and click Advanced.
• Go to the DNS tab.
  • If the automatic DNS settings are not working, there are a couple manual DNS entries that you can use.
    • 4.2.2.1 or 4.2.2.2 is a public DNS server.
    • There is also OpenDNS: 208.67.222.222 or 208.67.220.220

If manual configuration isn't working either, continue to the next section.

Proxy Settings

Proxy settings can be manually configured for both specific browsers and for the operating system in general. More often, however, malicious software such as spyware will inject its own proxy settings without the user being aware.

We can easily fix this, however if you do find bizarre proxy settings it is usually a good idea to do a full-system antivirus scan afterwards.

Windows

• First check the Global Proxy Settings, which are located in Settings. Open up Settings, click Network & Internet, then select the Proxy tab.
• The proxy will be listed here. Disable the proxy server if you see one there, and furthermore you can record the proxy address if you're interested in following up on the origin of the malware.
• Check the browser proxy settings specific to the browser being used.
  • If it's Edge, you are already done.
  • Firefox's proxy settings are located under Options > General > Network Settings.
  • Google Chrome's proxy settings are located under Settings > Advanced > Privacy and Security > Open proxy settings

macOS

• Proxy settings for can be found in System Preferences > Network > Advanced > Proxies.
• You can also check local browser settings via the windows method above.

Third-party Firewall: check for friendly network-layer software

Often times there can be third party software such as firewalls, anti-virus, or anti-spyware programs where the security level either set incorrectly or simply too high, and it is blocking the outgoing network traffic. This is mostly common on windows machines but it is also possible on macOS as well. Unfortunately there's no one single straightforward method of identifying this problem because there is so much software out there.

For Windows machines, you can boot into safe mode with networking by pressing F8 on start up.

If the Internet connection is working fine in safe mode and not in regular mode, there is a decent chance that certain software is blocking the connection, because said software will not be running in safe mode. Usually the best way to identify what could be blocking traffic is to boot back into regular mode, and check every program running in the system tray. Anything that is anti-virus, anti-spyware, or firewall related could be the culprit.

On macOS, this software would most likely present itself either in the menu bar at the top of the screen, or at the very bottom of System Preferences.

Once you have identified any type of antivirus, anti-spyware, or firewall software running, start by disabling the software altogether.

• If this repairs the connection, you can narrow down your search by re-enabling the software and going through some of the settings.
• Check specifically for firewall or traffic blocking settings, try disabling them or lowering the security level.

If disabling the software altogether has no effect, continue to the next section.

Malware: check for malicious network layer software (Windows)

Equally common (though perhaps more common) to friendly firewall software are malicious forms of malware: viruses, or spyware, which either block or re-direct your network traffic. Anything malicious of this nature can be interfering with your network interface and cause all sorts of problems. Contact the Technology Service Desk for help removing malware.

If the machine comes up clean, or the removal of malware did not put the network connection back into a working state, it is possible that the registry still has remaining corruptions due to present or previous malicious software. Contact the Technology Service Desk for help.

WinSockFix is an incredibly useful tool that deserves a special mention here because it specifically locates network-related registry entries and attempts to fix them. WinSockFix is available from Softpedia here.

Network Equipment: check local network equipment for problems

The problem can often lie in the switch, router, or modem that your system is connected to. If you have access to this hardware, here are common things to check to ensure that the network equipment is functioning properly.

• Perform a basic power cycle of the router. Unplug the power cable from the wall and wait for five minutes. The reason to wait is so that all the temporary memory is cleared and potentially erroneous data is wiped.
  • If a cable modem is involved as well, perform the same power cycle on the modem.
• Check the router's configuration to make sure the DHCP server is enabled. Usually the router configuration can be accessed by opening a web browser and navigating to http://192.168.1.1 or http://192.168.0.1, depending on the type of router. Once in the configuration look for a setting for the DHCP server, and make sure it is running.
• Check the router's configuration for high-security firewall settings. Some routers have an extra firewall layer that is usually unnecessary if you are running an operating system-level firewall. Try disabling this or reducing the security level.
• Check the router's Wi-Fi configuration. Sometimes due to interference you may need to change the wireless frequency (referred to as a channel) to get a clearer signal.
• Failing all of the above, most routers allow you to reset the configuration to factory settings. Usually you may do this through an option in the HTML configuration page, or by pressing and holding the Reset physical switch on the back of the router for a certain amount of time. Look this up for the model router before trying it.
• Note: Additionally, you can upgrade the routers firmware to the latest version. On very old routers there can sometimes be disagreements with newer network cards. 

Contact ISP or Network Administrator

If you are confident that your software configuration is in check and have tried resetting the network equipment, its always possible that the external uplink is having issues. Try contacting the nearest network administrator if this is a business or commercial setting, or the service provider in a residential setting.

Device Drivers: re-install network device drivers (Windows)

At this point we have ruled out most of the common software issues that you are likely to ever see. Its possible now that either the hardware itself is broken or the driver has been messed up in some manner. The best way to resolve this is to download the latest official driver from the manufacturer and install it.

• Find out the specific model of your computer. Example: Dell Inspiron E1500, or Sony Vaio VPCCW21FX/L
• Go to the manufacturer's website, find the Software Drivers & Downloads section, and enter in the model of your computer.
• Find the specific network driver you need. Make sure if the problem is with Wi-Fi that you get the Wireless Card driver, and if it's with the wired connection, make sure you download the broadband or Ethernet driver. Make absolutely sure that you get the latest driver (look at the date!)
• Once the driver is downloaded, there are two ways to approach installing it
  • The simplest way is to just run the installer for the driver, and overwrite the existing driver. Once it's installed, restart the computer and test the connection.
  • The manual way to install the driver is to first remove the existing driver configuration.
    • Right-click This PC and go to Properties
    • Go to Device Manager. On Windows 10, Device Manager is on the sidebar.
    • Find the Ethernet or wireless card device that you wish to fix, right click it and click Uninstall
    • You will be prompted immediately that new hardware has been found; if not, restart the computer to activate the prompt.
    • Within this prompt you can point to a location of the driver file for the hardware device. Point to the downloaded driver file(s).

Hardware: re-seat or replace network card hardware

It's always possible that the hardware itself on the network card is faulty. This is likely if the problem presents itself seemingly randomly or intermittently. The first thing to try is simply re-seating the card. This is obviously much easier on a desktop computer than a laptop but the same idea applies to both. This guide will not go into too much depth on the hardware side of things.

If you can get access to the card, either by removing the side case of a desktop or the top case of a laptop, try pulling out the card from its slot completely and then plugging it back in firmly. If there are screws, make sure that they are secured tightly and that the card does not move at all if you wiggle it gently.

Failing this, the card may need to be replaced with a new one.

Additional Assistance

Contact the Technology Service Desk for assistance.