Troubleshooting Wi-Fi

Wireless networks are a real boon when they work right, but they can also be one of the most vexing things to troubleshoot when they don't. Let's turn to some practical advice on how to detect and correct wireless hardware, software, and configuration problems. As with any troubleshooting scenario, your first step in troubleshooting a wireless network is to break down your tasks into logical steps. Your first step should be to figure out the scope of your wireless networking problem. Ask yourself who, what, and when:

• Who is affected by the problem?
• What is the nature of their network problem?
• When did the problem start?

The answers to these questions dictate at least the initial direction of your troubleshooting. So, who's affected? If all machines on your network-wired and wireless-have lost connectivity, you have bigger problems than the wireless machines being unable to access the network. Troubleshoot this situation the way you'd troubleshoot any network failure. Once you determine which wireless nodes are affected, it's easier to pinpoint whether the problem lies in one or more wireless clients or in one or more access points.

After you narrow down the number of affected machines, your next task is to figure out specifically what type of error the users are experiencing. If they can access some, but not all, network services, then it's unlikely that the problem is limited to their wireless equipment. For example, if they can browse the Internet but can't access any shared resources on a server, then they're probably experiencing a permissions-related issue rather than a wireless one.

Finally, determine when the problem started. What has changed that might explain your loss of connectivity? Did you or somebody else change the wireless network configuration? For example, if the network worked fine two minutes ago, and then you changed the WEP key on the access point, and now nobody can see the network, you have your solution-or at least your culprit! Did your office experience a power outage, power sag, or power surge? Any of these might cause a WAP to fail.

Once you figure out the who, what, and when, you can start troubleshooting in earnest. Typically, your problem is going to center on your hardware, software, connectivity, or configuration.