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"The Wi-Fi sucks” or “the Wi-Fi is down”. These words are the bane of every wireless engineer's existence. Users often don't know the difference between a true Wi-Fi issue and a general network issue that LOOKS like a Wi-Fi issue. To the average user, because Wi-Fi is how they access the entire network, there is no difference in their mind between the wireless and wired portions of the network. DHCP, DNS, AAA, none of that means anything to the average user.

You can't blame them either, because it's not their job to know. That's why network engineering is a viable career path. All the user knows is that trying to access whatever resource they need to do their job has become a pain in the posterior and they want it fixed yesterday. So how do wireless engineers discern where the problem actually lies? Like all good troubleshooting it starts by asking good questions: "Are only wireless clients experiencing this issue?" It sounds simple but that one question can save a ton of troubleshooting effort. If the answer is "no" then you can rule out anything related to the RF as the root cause because a wired device isn’t impacted by the RF environment.

If the answer is "yes", it still might not truly be a wireless issue. Why? Because there are all sorts of network configurations on the wired side that are required for wireless clients to be able to access the rest of the network. For example, it’s a common best practice to place Access Points in a dedicated VLAN and subnet. If the VLAN the APs are assigned to gets removed from the switch, every client connected to one of those APs is going to lose network connectivity because the APs can’t forward traffic to the rest of the network without being assigned to a VLAN. If they’re controller based or “lightweight” APs, they generally won’t even be able to broadcast their SSIDs because without a VLAN assignment they won’t be able to join a WLC to get their configuration. Users will see this as "the Wi-Fi is down", even though the actual problem is a misconfig on the switch.

Now hopefully you won’t have some buffoon obliterating VLANs from the switch for no reason, but this is just one example of a config that technically isn’t related to the wireless environment that is required for Wi-Fi to work. That means another important question to ask is some variation of, “are all the necessary wired side configurations in place for the wireless clients, APs, and WLC to talk to the rest of the network?” To get more specific, are the necessary VLANs in place? Are the ports going to the APs and WLC configured correctly? Are those ports in the correct VLANs, or are the necessary VLANs allowed on the trunk? Are the correct protocols and ports necessary for the AP and the WLC to talk to each other allowed on the firewall? Is the wireless traffic being routed properly? Can the APs and wireless clients reach the DHCP server? These are just a few examples of questions you may need to ask to determine what is really causing a supposed “Wi-Fi issue”.

Finally, one question that you should always ask, for any networking issue not just wireless, is “what changed?” Because I promise you, if it was working fine yesterday and it’s broken today, SOMETHING changed. Now whether that something is an upgrade, a config change, or different user activity is what you’ll have to determine. Nonetheless, nothing begins to exist without a cause and that includes network problems. So the next time a user tells you the “Wi-Fi sucks”, get ready to drill deeper, because there’s a good chance it’s not the Wi-Fi at all. It might be somewhere else in the network, and it’s your job to figure out where.