In this article, we’ll share with you all the important things you need to know to efficiently maintain and troubleshoot a wireless LAN. In this first part of the two part series, we will start off by discussing system maintenance on a WLC (Wireless Lan Controller), AP (Access Point), and WCS (Wireless Control System).
Then we’ll proceed to share with you a tested and proven troubleshooting model. We’ll also take up some common issues and their corresponding mitigation steps.
You can obtain the version of your existing code by using any of the following series of steps:
Through the Wireless LAN Controller:
Through the command line:
After knowing which version of the code you currently have, the next step is to determine what available version of the code is that you can upgrade to. This is done through www.cisco.com. Note that you can only download the appropriate code from there if you have both a cisco.com user ID and a valid Cisco SMARTnet service contract. If you have those two, then you can proceed as follows:
We now go to the final step, which is the upgrading process itself. Again, there are three ways you can do this: through a command line interface, the WCS web interface, or the WLC web interface.
Using the WLC web interface – If you want to use the WLC web interface in performing the upgrade, make sure you activate the TFTP server first. When it’s ready, go to the WLC web interface and go to Commands and enter/select the following settings:
When you’re done, click the Download button. You can monitor the ensuing process through the TFTP server or the Wireless LAN Controller console. Configuration backup/restore Whenever you arrive at an equipment configuration that lets your wireless system run smoothly, it’s advisable to perform a backup on that configuration. That way, you can quickly and easily restore it in the future in the event that that particular equipment’s configuration somehow gets messed up.
Backing up and restoring is very similar to the process of uploading and downloading code. The main difference is that, instead of dealing with a code file type, you’ll be dealing with configuration file types. So, for example, in the WLC web interface, instead of selecting Code from the File Type drop-down list, you need to select Configuration.
Configuration backup using the WLC web interface:
Configuration restore using the WLC web interface:
When you’re done, click the Download button. You can monitor the ensuing process through the TFTP server or the Wireless LAN Controller console
Both the WLC and the WCS are equipped with alarms and monitoring features. However, because the main purpose of the WLC is really designed for supervising and configuring access points, it doesn’t have as many alarms and system monitoring features as the WCS.
WLC Alarms and system monitoring – The alarms on the WLC come only in the form of crash logs, message logs, core dumps, AP crash logs, and other log outputs, which are accessible via the Management menu (at the top of the screen).
WLC monitoring functions, on the other hand, are mostly available under the Monitor menu and they deliver snapshots of information such as the controller’s health, access point status, wireless system statistics, clients that are currently active, and a rogue access point summary. WCS alarms and system monitoring – Here you can find a more extensive selection of alarm functions. For instance, it has a more detailed log output, which is available via the Alarms section under the Monitor menu. In the Alarms section, you may see a list of rogue access points along with relevant information such as their MAC address, name, SSID, channel, and many others.
WCS monitoring functions, on the other hand, are immediately available on the WCS home screen dashboard. They are shown on tabs like:
In order to deal with wireless issues effectively and efficiently, you need to approach each problem with a deliberate, thought-out methodology. This is where a troubleshooting model comes into play. The 8-point model outlined below is adopted from some of Cisco’s documentation and educational pursuits and is very applicable in the wireless environment.
The Troubleshooting Model:
Define the Problem When a user complains that “the network’s slow”, you need to make sure that the network is really the problem, and it’s not because somebody is just downloading a large file or that the complainant’s PC is actually the one that’s problematic. And even if the problem is really the network, you still need to pin down exactly where the problem lies before you can proceed to the next step.
Gather the Facts Ask as many relevant questions as you need. Try to find out for example: when the problem started occurring; whether the problem is broad or localized; whether other users are experiencing the same problem; etc.
Document the Facts As you proceed with your investigation, record all the facts. This can be helpful when you start considering the possibilities. If you won’t be able to recall all the relevant information when it’s time for the next troubleshooting step, you could end up unnecessarily repeating steps you’ve already taken.
Consider the Possibilities Based on the facts collected, try to analyze and see what the possible causes may be. This is where you’ll be able to realize the benefits of good documentation. When it’s time to consider the possibilities you will be able to do so from an informed perspective by looking at the documented data.
Create an Action Plan If one possible cause stands out, draw up an action plan to tackle that one. It’s always best to tackle one possible cause at a time.
Repeat Until Resolution If your action plan worked, then you’re done. You can proceed to the next step. However, if the problem still persists, go back to considering the possibilities.
Document the Solution This part is useful because you can use the documented solution in case a similar complaint is brought up in the future.
Common Issues and Mitigation Steps While there are certainly a lot of wireless issues out there, the ones we’ve featured below are some of the most common. We’ve grouped them in terms of client issues, access point/WLAN issues, and controller issues. Client issues
Of all three groups of issues, client issues are probably the most common. This is because end users are mostly non-technical people and hence may not know how to resolve simple problems by themselves. Here are some of those issues along with the possible causes and their corresponding solutions. Issue: Client cannot connect to the AP/WLAN Possible causes and their corresponding solutions:
Issue: Client is not receiving an IP address Possible causes and their corresponding solutions:
Possible causes and their corresponding solutions:
Issue: Clients are complaining about performance Possible causes and their corresponding solutions:
Issue: Traffic from WLAN unable to reach wired network through controller Possible causes and their corresponding solutions:
Like we said earlier, this is by no means an exhaustive list. There are certainly more wireless issues out there. But we hope this list can help you get a feel of the kind of issues you may later on encounter.
This concludes part 1 of this two-part series. In part 2 we will discuss some tools for problem identification and resolution System maintenance typically involves any of the following tasks: upgrading system code, backing up or restoring configuration, and using alarms and system monitoring tools. There are a couple of steps you need to go through to achieve that, which we will walk you through.