Troubleshooting Networks | CompTIA A+ 220-1001 | 5.7

In this video you will learn about common issues associated with wired & wireless networks.


No Connectivity

For no connectivity errors:

  • Try connecting with another device to verify that there is actually a problem with the network and not the device trying to connect to the network.
  • If using WiFi, make sure that the WiFi is enabled & that you are connected to the proper SSID using the correct password.
  • Check to make sure that the network cables are properly connected and then look for solid green link lights which indicate that there is connectivity.
  • Check the power supply going to the hub, switch, wireless access point, or router.  Unplug it, wait about a minute or two, then plug it back in to restart the device.

APIPA/Link Local Address

APIPA & link local addresses are assigned to devices if the device is unable to reach the DHCP server (which assigns IP addresses). In most SOHO environments, the DHCP is usually the router. Check to see if the router is working properly and if so, then restart the computer/device to see if it gets assigned an IP address from the DHCP. If the problem persists, check for a bad cable or inability to connect to a wireless network.

To diagnose network problems pertaining to certain operating systems, do the following:

  • Windows 7: Open the Network and Sharing Center and click the red X in the Internet Connection dialog to launch the Internet troubleshooter.  Use the troubleshooter and follow its recommendations.
  • Windows 8/8.1: Use Search to locate and start the Internet troubleshooter.  Use the troubleshooter and follow its recommendations.
  • Windows 10: Click the network icon in the taskbar to open the Network Status window.  If not connected, a β€œtroubleshoot” button appears.  Click it to start the Internet troubleshooter.  Use the troubleshooter and follow its recommendations.
  • Connection problems with any OS: Turn off the broadband modem, access device, or router, wait about a minute, and then turn it back on. If the problem was with the broadband modem/access device, this should solve the problem.  If it doesn’t, contact the ISP as the problem might be on the ISP network.
  • If only one device is affected, disconnect from the wireless network and reconnect to it.  For a wired network, restart the computer.

Intermittent Connectivity

Intermittent connectivity issues can be caused by:

  • Dead spots (poor signal) on a wireless network:  Relocate the wireless router.
  • Too many networks using the same channel:  Use a wireless network scanning device or app to find a channel with less traffic. Then reconfigure the network to use that channel.
  • EMI or RFI interference:  Alarm systems, elevators, fluorescent lights, and motors can interfere with wired networks running UTP.  Switch to STP cable or relocate cables away from interference.
  • Defective network cables:  Replace the cables.
  • Contact your ISP:  Contact the ISP after troubleshooting your local network if connection problems persist.

IP Conflict

IP conflicts arise when two devices are on the same network trying to use the same IP address. When this happens, neither device will be able to connect to the network. IP conflicts tend to happen when a DHCP server assigns an address to a device that has already been manually assigned to another device or when an admin assigns an address to a device that is already in use. To avoid IP conflicts, configure devices with manual IP addresses to use a different range of addresses than those used by the DHCP server.

Slow Transfer Speeds

Slow transfer speeds can be caused by a variety of reason, some of which are:

  • Damage to cables & connectors:  Check cables for damage.
  • High-speed NICs connecting to low-speed switches:  When using Gigabit Ethernet switches and routers, confirm that all networking devices meet Gigabit Ethernet standards (CAT 5e or 6, 6a, 7 cable) and are configured to use Gigabit Ethernet.
  • RFI/EMI interference:  Wireless house phones & microwave ovens can cause interference with wireless networks. If your router is located near these devices, relocate the router to another spot. Switch to a wireless router that uses the 802.11ac standard and use the 5GHz band to avoid this type of interference.

Low RF Signal

Low RF signals on a wireless network can be caused by:

  • Interference from other wireless networks:  Use a wireless network analyzer to determine the least-used channels for the network and switch to one of those channels.
  • Concrete walls:  Relocate the router. If it is not possible, add repeaters (wireless or powerline).
  • Adjustable router or NIC antennas in improper positions:  Follow manufacturer recommendations for proper antenna placement.

SSID Not Found

If the SSID on the router has been configured to not broadcast its name, a user trying to connect will have to know the name of the network and the encryption key (password). If an SSID not found error is displayed (either by name or as a hidden network), reboot the router. If rebooting the wireless router doesn’t help, open up the router’s configuration web page (IP address for most SOHO routers) to verify that it is configured as a router. Change and save the configuration and then try the connection again.