Chapter 22. Troubleshooting Wired and Wireless Network Problems
This chapter covers the following A+ 220-1001 exam objective:
• 5.7 – Given a scenario, troubleshoot common wired and wireless network problems.
Here we have the last of the 220-1001 troubleshooting chapters. In this chapter we’ll discuss troubleshooting network connectivity issues. Because you will have users that connect in a wired fashion and other users that connect in a wireless fashion—and some connecting both ways—you have to be ready to support a variety of network connectivity. The goal of this chapter is to explain some basic troubleshooting techniques in a more generic sense—meaning, less step-by-step procedures and more of the troubleshooting mindset that you should maintain. To perform their work, users need access to resources, and network connectivity enables this. So, a faulty network connection means little to no available resources; and consequently, little to no work getting done. This should help to stress the importance of network connectivity.
5.7 – Given a scenario, troubleshoot common wired and wireless network problems.
ExamAlert
Objective 5.7 concentrates on troubleshooting common symptoms of wired and wireless network problems, such as: limited connectivity; intermittent connectivity; no connectivity; unavailable resources; APIPA/link local addresses; IP conflicts; slow transfer speeds; low RF signal; and SSID not found.
Troubleshooting Common Symptoms
Network troubleshooting? Oh yes, it could be the best way to learn. First, I recommend reviewing the CompTIA troubleshooting theory in Chapter 17, “Computer Troubleshooting 101.” Second, for successful troubleshooting, remember to check the simple and obvious first. Power connections, network connections, and so on are common culprits for network problems.
It’s all about access to resources. If a resource—be it a data share or printer, or whatever—is unavailable, then the user won’t be able to get his or her work done. Efficiency decreases, and the organization loses money. Resources can be broken down into two types: local resources—meaning ones on the LAN; and remote resources—ones that are beyond the LAN, possibly on the Internet or another external network.
• Local resources: You might find that a user can’t browse the network or map network drives to network shares, or connect to network printers, or access an e-mail server on the LAN. There are lots of examples, but the bottom line is this: if a user can’t access local resources, then the network connection needs to be troubleshot. That’s the bulk of what we discuss in the following bullet points. If multiple users can’t access resources, then it could be a more centralized problem. For example, a server is down; perhaps a DHCP server is not properly handing out IP addresses to clients, or a domain controller has failed, and users cannot be authenticated to resources. As a technician with the A+ certification, this might go beyond the scope of your work, so be prepared to escalate the problem if necessary.
• Internet-based resources: If remote resources are not available to a user; for example, websites, VPN connections, and streaming media services, then it could be that the IP configuration (especially the gateway and DNS settings) needs to be inspected and possibly reconfigured. If multiple users are having connectivity problems, then it could be the gateway itself or the DNS server that needs to be fixed (among other things). Again, escalate the problem if necessary.
All of the following bullets can lead to unavailable resources, either locally, or on the Internet. Let’s discuss some symptoms you might encounter and how to troubleshoot the underlying problems.
• No connectivity: If a user complains of a problem connecting to the network and you verify that there is indeed a problem, check that patch cable first and verify there is a link light. Make sure the user’s computer is actually connected to the network. If it appears to be a cable issue, use a patch cable tester or cable certifier to test the cable. If it isn’t a cable problem, make sure the network adapter is enabled. If it’s a laptop and the user has wireless, check the Wi-Fi switch or button. Next, run an ipconfig /all and check the settings. Afterward, ping the local computer to see if TCP/IP works. If you haven’t resolved the problem by now (and you probably will), access the Network and Sharing Center in Windows and view the graphical connections to see if there is a red x anywhere denoting a problem. Use the network troubleshooter if necessary. You can also right-click the Network icon in the Notification Area and select Troubleshoot problems. This brings up the Windows Network Diagnostics program; follow the steps for a possible resolution. Check for the latest drivers for the network adapter. You can also try rebooting the computer to find out from the user if any programs were recently installed or updated. Sometimes antivirus software or firewall updates can cause connectivity issues. Some switches and routers have the capability to enable/disable specific ports; make sure the port in question is enabled in the firmware. If a network-wide problem, power down the network equipment (SOHO routers, cable modems, and so on); then disconnect the network and power cables and wait 10 seconds. Finally, reboot the network equipment. If users cannot find the wireless network that they need to connect to using Windows or the wireless adapter’s software, there are third-party Wi-Fi locator programs that can be downloaded for free. These will locate all wireless networks in the vicinity and display SSID, signal quality, distance, and channel used (as long as the wireless network adapter is functional). If an SSID does not show up in Windows or in third-party software, you should enter the SSID manually.
• Limited and intermittent connectivity: If the problem is limited connectivity, attempt some pings. First, ping the localhost to see if TCP/IP is functioning. If that works, ping the router or another system on the network. If that fails, then the user only has local connectivity. Run an ipconfig /all and check the rest of the IP settings. If pinging the router did work, try pinging a website by domain name. If that fails, then the DNS server address is probably not configured properly. Check it with an ipconfig /all and modify in the IP Properties dialog box if necessary. Run an ipconfig /release and /renew if you suspect an issue with obtaining an address from a DHCP server. Intermittent connectivity could be caused by a faulty patch cable, wireless network adapter that is too far away from the WAP, or a router that needs to be reset. In a larger environment, if a person can access some networks but not others, you might want to try a tracert to inaccessible networks to see where the problem lies. This type of network troubleshooting gets a bit more in depth, but the tracert program will basically show which router between you and the final destination has failed.
• Slow transfer speeds: The type of Internet connection is going to be the biggest contributor to this. If a user has dial-up and complains about slow transfer speeds, it’s time to upgrade! Even though dial-up can be tweaked for speed, it’s simply easier to move up to DSL, cable, or fiber-based services. Slow transfer speeds could also be caused by the network equipment, patch cables, and network adapter. The newer and faster the equipment and cables, the better the data transfer rate. Of course, slow speeds could also be caused by network congestion. Run a netstat -a to see which types of connections the local computer has to the Internet currently. If you see dozens of connections, the computer might be compromised by malware or be part of a botnet. Or perhaps the user runs torrent software or just goes to a lot of websites for various reasons. Check the router as well. See what kind of traffic is passing through it. Update everything, clear all cache, power cycle all equipment, and you just might see an improvement.
• Low RF signal: A low radio frequency signal spells doom for wireless users. The first thing to check is the distance of the computer from the WAP. Make sure the computer is within the appropriate range. If the WAP uses 802.11ac and the wireless adapter is 802.11g, consider upgrading to an 802.11ac adapter. Update the software on the wireless adapter and WAP as well. Placement of the router is important; it should be central to all users and away from sources of EMI. Try different antenna placement on the router and the wireless adapter. Normally, the 90-degree angle is best, but a little tweaking can go a long way. Also, some routers can boost their wireless signals. Check for this setting in the firmware.
• IP conflict: An IP conflict message will pop up on the displays of both Windows computers that are causing the conflict. Usually, the first computer that used the IP address will continue to function, whereas the second computer will not be able to access the network. The second computer will have to be reconfigured to a different IP address and rebooted. Reboot the first computer for good measure. IP conflicts usually happen only when static IP addresses are being used. If this is the case, consider using DHCP for all client computers.
• Link-local/APIPA address: If a computer is showing an IPv4 link-local address such as 169.254.49.26 when you type ipconfig /all, it generally means that the computer is attempting to obtain an IP address from a DHCP server but is failing to do so. IPv4 link-local addresses always start with 169.254. Microsoft also uses the name Automatic Private IP Addressing (APIPA). Usually, a link-local address is assigned internally, so the real problem could be that the computer is not getting connectivity to the network. Check everything in the first bullet point. Also, consider using ipconfig /release and /renew. Finally, if these do not work, check the DHCP server to make sure it is functional and available.
ExamAlert
Double-study your troubleshooting techniques! It’s all about troubleshooting!
Cram Quiz
Answer these questions. The answers follow the last question. If you cannot answer these questions correctly, consider reading this section again until you can.
1. A user complains that the computer is not connecting to the network. Which of the following should be done first?
A. Use ipconfig /all.
B. Ping the router.
C. Check the patch cable.
D. Check the network drivers.
2. One computer loses connectivity. All connectors and settings appear to be correct. Which tool should be used to fix the problem?
A. Multimeter
B. PSU tester
C. Loopback plug
D. Cable tester
3. One of your customers no longer has access to a frequently accessed website. You ping another computer and the router on the network successfully. Which of the following should be done next?
A. Check the IP configuration.
B. Ping the website.
C. Update the OS.
D. Update the AV software.
4. A user moves a laptop from one office to another. The patch cable and the network adapter do not appear to be working properly at the new office. The cable is plugged in correctly and tests okay when checked with a patch tester. Which of the following should be done first?
A. Check whether the port on the switch is enabled.
B. Update the network adapter driver.
C. Replace the patch cable with a crossover cable.
D. Make sure the network adapter is compatible with the OS.
Cram Quiz Answers
1. C. Check the super-obvious first. Make sure the computer has a physical cabled connection to the network. Then attempt things such as ipconfig, ping, and network driver updates.
2. D. Use a patch cable tester to check the patch cable and possibly use a continuity tester to test longer network cable runs. Multimeters are great for testing wires inside the computer or AC outlets, but they are not used for network troubleshooting. A PSU tester tests power supplies. The loopback plug will verify whether the local computer’s network adapter is functional.
3. B. This is the concept of pinging outward. Start by pinging the localhost, then a computer, and then the router on the network. Then ping a domain name or website. If you can ping the website but the browser cannot get through, the browser might have been compromised. If you cannot ping the website, you should check the IP configuration; the DNS server address might be incorrectly configured. Updating the OS and AV software should be done right away if you guess that the browser has been compromised.
4. A. Some routers and switches can disable physical ports (a smart security measure). Check that first. Later, you can check whether the network adapter is compatible with the OS and update it if necessary. Do not replace the cable with a crossover; those are used to connect one computer to another.