Troubleshoot WLAN Issues
In the previous topics, you learned about WLAN configuration. Here we will discuss troubleshooting WLAN issues.
Network problems can be simple or complex, and can result from a combination of hardware, software, and connectivity issues. Technicians must be able to analyze the problem and determine the cause of the error before they can resolve the network issue. This process is called troubleshooting.
Troubleshooting any sort of network problem should follow a systematic approach. A common and efficient troubleshooting methodology is based on the scientific method and can be broken into the six main steps shown in the table.
|1||Identify the Problem||The first step in the troubleshooting process is to identify the problem. While tools can be used in this step, a conversation with the user is often very helpful.|
|2||Establish a Theory of Probable Causes||After you have talked to the user and identified the problem, you can try and establish a theory of probable causes. This step often yields more than a few probable causes to the problem.|
|3||Test the Theory to Determine Cause||Based on the probable causes, test your theories to determine which one is the cause of the problem. A technician will often apply a quick procedure to test and see if it solves the problem. If a quick procedure does not correct the problem, you might need to research the problem further to establish the exact cause.|
|4||Establish a Plan of Action to Resolve the Problem and Implement the Solution||After you have determined the exact cause of the problem, establish a plan of action to resolve the problem and implement the solution.|
|5||Verify Full System Functionality and Implement Preventive Measures||After you have corrected the problem, verify full functionality and, if applicable, implement preventive measures.|
|6||Document Findings, Actions, and Outcomes||In the final step of the troubleshooting process, document your findings, actions, and outcomes. This is very important for future reference.|
To assess the problem, determine how many devices on the network are experiencing the problem. If there is a problem with one device on the network, start the troubleshooting process at that device. If there is a problem with all devices on the network, start the troubleshooting process at the device where all other devices are connected. You should develop a logical and consistent method for diagnosing network problems by eliminating one problem at a time.
Wireless Client Not Connecting
When troubleshooting a WLAN, a process of elimination is recommended.
In the figure, a wireless client is not connecting to the WLAN.
If there is no connectivity, check the following:
- Confirm the network configuration on the PC using the ipconfig command. Verify that the PC has received an IP address via DHCP or is configured with a static IP address.
- Confirm that the device can connect to the wired network. Connect the device to the wired LAN and ping a known IP address.
- If necessary, reload drivers as appropriate for the client. It may be necessary to try a different wireless NIC.
- If the wireless NIC of the client is working, check the security mode and encryption settings on the client. If the security settings do not match, the client cannot gain access to the WLAN.
If the PC is operational but the wireless connection is performing poorly, check the following:
- How far is the PC from an AP? Is the PC out of the planned coverage area (BSA)?
- Check the channel settings on the wireless client. The client software should detect the appropriate channel as long as the SSID is correct.
- Check for the presence of other devices in the area that may be interfering with the 2.4 GHz band. Examples of other devices are cordless phones, baby monitors, microwave ovens, wireless security systems, and potentially rogue APs. Data from these devices can cause interference in the WLAN and intermittent connection problems between a wireless client and AP.
Next, ensure that all the devices are actually in place. Consider a possible physical security issue. Is there power to all devices and are they powered on?
Finally, inspect links between cabled devices looking for bad connectors or damaged or missing cables. If the physical plant is in place, verify the wired LAN by pinging devices, including the AP. If connectivity still fails at this point, perhaps something is wrong with the AP or its configuration.
When the user PC is eliminated as the source of the problem, and the physical status of devices is confirmed, begin investigating the performance of the AP. Check the power status of the AP.
Troubleshooting When the Network Is Slow
To optimize and increase the bandwidth of 802.11 dual-band routers and APs, either:
- Upgrade your wireless clients – Older 802.11b, 802.11g, and even 802.11n devices can slow the entire WLAN. For the best performance, all wireless devices should support the same highest acceptable standard. Although 802.11ax was released in 2019, 802.11ac is most likely that highest standard that enterprises can currently enforce.
- Split the traffic – The easiest way to improve wireless performance is to split the wireless traffic between the 802.11n 2.4 GHz band and the 5 GHz band. Therefore, 802.11n (or better) can use the two bands as two separate wireless networks to help manage the traffic. For example, use the 2.4 GHz network for basic internet tasks, such as web browsing, email, and downloads, and use the 5 GHz band for streaming multimedia, as shown in the figure.
The figure depicts a home network splitting the traffic between 2.4GHz and 5GHz. The WLC is connected to a television, cell phone and tablet using 5GHz. It is also connected to two laptops using 2.4 GHz.
There are several reasons for using a split-the-traffic approach:
- The 2.4 GHz band may be suitable for basic Internet traffic that is not time-sensitive.
- The bandwidth may still be shared with other nearby WLANs.
- The 5 GHz band is much less crowded than the 2.4 GHz band; ideal for streaming multimedia.
- The 5 GHz band has more channels; therefore, the channel chosen is likely interference-free.
By default, dual-band routers and APs use the same network name on both the 2.4 GHz band and the 5 GHz band. The simplest way to segment traffic is to rename one of the wireless networks. With a separate, descriptive name, it is easier to connect to the right network.
To improve the range of a wireless network, ensure the wireless router or AP location is free of obstructions, such as furniture, fixtures, and tall appliances. These block the signal, which shortens the range of the WLAN. If this still does not solve the problem, then a Wi-Fi Range Extender or deploying the Powerline wireless technology may be used.
Most wireless routers and APs offer upgradable firmware. Firmware releases may contain fixes for common problems reported by customers as well as security vulnerabilities. You should periodically check the router or AP for updated firmware. In the figure, the network administrator is verifying that the firmware is up to date on a Cisco Meraki AP.
On a WLC, there will most likely be the ability to upgrade the firmware on all APs that the WLC controls. In the next figure, the network administrator is downloading the firmware image that will be used to upgrade all the APs.
On a Cisco 3504 Wireless Controller, Click the WIRELESS tab > Access Points from the left menu > Global Configuration submenu. Then scroll to the bottom of the page for the AP Image Pre-download section.
Users will be disconnected from the WLAN and the internet until the upgrade finishes. The wireless router may need to reboot several times before normal network operations are restored.