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Mar 02

Anatomy of a WiFi Fault

Anatomy of a WiFi Fault

Over the years we have dealt with a large amount of bugs in controller code, old drivers on devices, chipsets that can’t roam properly, interference, rogue APs causing interference, incorrectly configured equipment and so on – the list of possible reasons for faults is a long one.

What makes faults even more difficult to fault find are intermittent ones - and WiFi is a tricky medium to debug and fault find.

Unlike a switch or router, where you control the medium and when you debug you see what's there - WiFi is an uncontrolled medium and you need special tools to do Air Sniffs and surveys - then you need to know how to interpret them,

So, How do we Approach a Fault to Find a Logical Conclusion?

The first thing to note, is that when we’re called in to analyse a fault, it's normally a complicated one - either it has been happening for a while, or multiple people haven't managed to get to the root cause. 

We come to the fault with many years experience, the right tools to measure the network and the right methodology.

Multi Layered Faults

And here’s the number one reason the fault hasn’t been fixed already: it's not one fault.

Yes, the majority of complex faults are actually a conglomeration of faults. You have several layered on top of each other, with the result being an almighty complex set of issues to sort out. There’s no silver bullet and changing and reverting one setting at a time is never going to fix the issue.

So, the question has to be: where do you start with a fault like this and how do you solve it? Let’s start at the beginning.

Fix your RF

Many faults are due to incorrect RF:

  • Not enough coverage (common – you’ve skimped on the number of APs)
  • Too many APs (you’ve got deep pockets and you’ve overcooked it)
  • Interference (why does everyone keep bringing in their own APs?)
  • You have a difficult RF environment (who designed all these brick walls)

So, you need to do a survey – confirm the status of the RF and check there’s enough overlap and not too much interference.


Setup your WLC

Check the WLC. Is the configuration correct? Confirm the WLC is setup with best practice and also to support the services you are running. Is the network power and channels tuned for the service you’re supporting? Have the SSIDs got the right sort of config for the services and devices you want to run? Have you got appropriate timeouts for AAA settings?

There's a lot of settings - and unfortunately, they're tuned to the services you're running, so there's no one size fits all. 

Check for Bugs!

Bugs exist, it’s a fact of life. If you’re at the end of your tether trying to work out why your network isn’t working properly... well maybe it’s a bug.

Bugs make the network do weird things – sometimes they are sporadic or triggered by a set of circumstances – by their nature, they’re hard to track down.If your network seems to be working fine for a while, then doesn't any longer a bug could be in play.

Conclusion: Anatomy of a WiFi Fault

The bottom line is that complicated faults can have more than one root cause. Keep an open mind and keep good records – from each change you make observe and record what happened – you may need to layer on several changes to fix up an issue.

If you can't fix it, that's where we come in - sometimes you just need to call in outside help to take a fresh look. 

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