…or how I’m spending my Easter Weekend
I’ve gone dark the past few weeks, or a month plus on the blogging, the Twitter, the Slack, the gym … ok maybe not the gym. Reason (not an excuse) is that I recently changed jobs and employers, and the change has forced my entire focus into the new gig (in a real positive way). Slacking off on all the other parts has been a bit of a drag. However, a wise man (@jockowillink) would say: new job taking time away from all the social media and the Interwebs; Good, it’ll create opportunities and be fodder for things to write about. So here we are, me full of fodder.
One of the perks of working for a manufacturer like Aruba, is the crates of lab gear that rolls on up to my door to build a home SE lab. I know my UPS driver, Rick, quite well after a month of near-daily visits. Setting up the catalogue’s-worth of gear is/has been a lot of fun, not to mention a great refresher and learning experience. I’ve always had a home lab, but now I have a Cadillac-grade lab (until my power bill comes in). Having a lab for so long, like most can relate, I have some legacy and older bits lying around. So when I fired up my shiny new Aruba Mobility Controllers I found myself connecting not only the latest and greatest Access Points, but for the heck of it, some older APs I had on the shelf. Thing is, a decade-old AP-105 can’t match a new AP-335 for performance, so what’s the point of having these old APs in service? Ahhh, why not do what you can’t often do at a customer site, convert them to full time Spectrum Monitors and see what I can see? The reason you don’t see APs deployed in a dedicated, non-client-serving mode typically is because customers are always budget conscious, and you get odd looks and head-shakes when you tell them you’d like to install APs that sit there and don’t serve clients. I know you can configure Aruba APs in Hybrid mode so they scan the client serving channel and serve clients, but I’m talking full-time, all-channel spectrum analysis.
Now why would this be valuable? When it comes to spectrum analysis – the Layer 1 (Physical) monitoring of the RF spectrum – there’s really two different ways to get it done. The first, and most common, is the “laptop” method, which means installing a special piece of software like Metageek’s awesome Chanalyzer, plug in a special WiFi adapter, and go walk around the area you want to scan. This works great when both the tool and the resource who has the specialized knowledge to operate and interpret results are located at the site you want to scan the spectrum. What happens when you have a distributed wireless network spread out over the entire province, or country, or world? That’s a lot of frequent-flyer miles for the laptop and the person using it. Not to mention, when you walk around with the laptop, you’re really only getting a “snapshot in time” view. What happens if the interference is intermittent, like the knocking under the hood of your car? Here’s where the value of infrastructure spectrum analysis comes in.
Here’s how I did it, and it’s actually really easy. Aruba Mobility Controllers operate in a lot of ways in a hierarchical manner. Once you get how everything connects up to the next layer, it’s pretty easy. A building block for the APs is the AP group. APs get assigned to an AP Group, which in turn points to and defines various parameters like the SSIDs it will serve, and common RF parameters. It’s under RF Management that you change on a per-radio basis the mode which the AP(s) in the group will operate. One trick that you have to watch for is to change and define a new Radio Profile to nest inside the AP Group, or you’ll end up modifying the default, and that’ll likely mess things up in other Groups:
And there you go, the MC will tell you it’s going to Apply and Reboot the APs, and once they come back up, they’re full-time Spectrum Analyzers. You can also convert an individual AP for a one-off by going into the AP’s spectrum override profile if you’re not into the whole AP Group thing.
Now that you’ve converted one or more APs into Spectrum Mode, it’s time to observe the data. Clicking the main Monitoring tab, and scrolling down to Spectrum Analysis, you get a new browser window pop up. When you first bring the Spectrum Dashboard tab up, there’s nothing running and when you try to view anything it tells you that no spectrum monitors are assigned. Have to fix that first under, surprisingly, the Spectrum Monitors tab, where you add the individual radios contained in the AP(s) that you assigned to the Spectrum Analysis AP Group:
Now we have a live AP, in Spectrum Analysis-mode, and it’s assigned to the Spectrum Analysis Dashboard – DISCO! Let’s see what it sees. Under the Spectrum Dashboard you’ll get a grid of four dashlets, and you have three different views in this format. Now here’s what I really like; you can completely personalize what you see, and the source. In the examples below I did the following: left-hand side was the 5 GHz radio, and the right-hand side was the 2.4 GHz radio.
- View 1: Real-time FFT & Swept Spectrogram
- View 2: Channel Metrics & Channel Summary Table
- View 3: Active Devices & Active Devices Table
All in all, there are fourteen different dashlet options that you can visualize various data views. Want to record the data over lunch time while you go grab a sandwich, salad and protein shake, just click Record, and when you come back, flip over to Playback View to see all that RF action you missed through your own Spectrum Analysis VCR.
So we have a pretty cool tool in the kit that allows us to flip an already deployed AP into an on-demand spectrum analysis collection client. If I’m in my command centre in Calgary, and there’s a problem I need to troubleshoot at a site in Grande Prairie, I can look at the physical Layer 1 spectrum directly through the already installed infrastructure without even leaving my desk. In my set-up, I can look in the Aruba AirWave management software I have and run historical reports on the RF health to match up to the spectrum analysis recording I took. Have fun!