APoS survey with Cisco 802.11ax APs

In case you hadn’t heard, Cisco has launched new Wi-Fi 6 (802.11ax) APs. This generally presents issues for those on the bleeding edge of doing Wi-Fi designs – especially if you rely on empirical data for your AP locations before hanging your APs. Cisco has a tendency to get gear out the door and usually enables site survey through autonomous (on 802.11ac wave 1 or earlier APs) or Mobility Express (read my writeup on 802.11ac wave 2 APs here) at a later date. The new Catalyst 9115, 9117, and 9120 APs are no exception. We know that Mobility Express is coming on these platforms, but between now and the time that we get Mobility Express for site survey mode, we’re very much out of luck.

We have a few customers that rely on empirical validation of their APs using APoS so we had to come up with a workaround. No, it’s not graceful, yes it’s a touch on the cumbersome side, but it works – and until we get the fully baked Mobility Express from Cisco, it’ll have to do…

Things you’ll need:

  • A real WLC running AireOS 8.9 code to support 802.11ax hardware (temporarily)
  • A wave 2 AP that can be dedicated to Mobility Express
  • 2x Site survey batteries
  • A console cable and this guide
  • Some network cables to hook it all up

This guide will walk you though configuring your 802.11ac wave 2 AP as a Mobility Express controller, then joining your 802.11ax AP to it so you can bring it’s radios up. Leveraging the built in WLC on the wave 2 APs running AireOS based Mobility Express, you can then configure radio power levels, channels, etc – all as needed for your AP on a Stick designs. You’ll need to carry two APs (and site survey batteries) with you, but for now – it’s what we have.

Start with a WLC running 8.9.100.0 (or a newer build that supports 802.11ax APs) and join your two APs to it. Ensure that your APs have the build on your WLC as both their primary and secondary images. Verify this using the ‘show ap image all’ command. This is important do to because once you have this all built out, you’re not going to have a lot of opportunity for monkeying with AP release images and you could save yourself some heartache if one of your APs decides to boot off of it’s secondary image. If you’re image numbers are different, use the ‘archive download-sw capwap <ap_image>’ command on your APs console to get it to update properly and reboot.

APs with same primary and backup

APs with same primary and backup

Once you get your AP image versions matched, take your 802.11ac wave 2 AP and convert it to mobility express for site survey using the guide I wrote previously. There are one or two things you should note when you’re doing this – we’ll be eventually using your 802.11ax AP as a subordinate AP to the one you’re now converting to Mobility Express and it won’t start it’s CAPWAP process without a pingable default-gateway. In this instance, we’ll have to make sure that, when we build our DHCP scope, we tell the scope option for the default gateway to be the IP address of the WLC – yes, even though the WLC can’t actually route packets. This will ‘fool’ the subordinate AP into thinking that the default gateway is reachable and will let it complete its eventual CAPWAP join. You’ll also want to make doubly sure that you’re converting it to the same release version of Mobility Express as is on your APs.

Match your default GW and WLC address

Once you have your converted 802.11ac wave 2 AP operational, hook it up to your first site survey battery, then hook your second site survey battery to your first using the ethernet (non-POE) interfaces. One you do this, you can hook your 802.11ax AP onto your second site survey battery POE interface to allow it to boot. You’re effectively creating a chain that goes AP <-> battery <-> battery <-> AP and using the ethernet passthrough for the master AP running Mobility Express to talk to the subordinate AP. Once all of your APs are up and talking to the Mobility Express controller, I’d recommend renaming the Mobility Express AP to WLC and the 802.11ax AP to ‘ap’ for the rest of the commands in the previous blog post to work properly.

Two batteries, two APs

802.11ax temporary rig, ready to go!

If you’re concerned about battery performance of your WLC AP, you can also issue the ‘config ap disable WLC’ (after you’ve renamed it properly) to save some power and to make it’s radios not show up in your survey!

Name your APs, disable the WLC AP!

Functional site survey!

Of course we’re looking forward to a complete Mobility Express instance to allow us to do site surveys with a single battery and AP, but until then, this will do if you’ve got the necessary parts and pieces!

4 Responses to APoS survey with Cisco 802.11ax APs

  1. brodie7838 says:

    Never seen ‘survey batteries’ like that before, would you mind sharing any info on them?

  2. Antonis_SP says:

    Also noting, that the .ax AP will continue to operate normally if the ME AP is disconnected and a WLANpi is connected, making active surveys possible.

    • scwifi says:

      Thanks for vetting that out! You’re correct that this should function as you’ve described. Having said that, any radio changes (channel or tx power) would need the ME AP re-attached to the 802.11ax AP to configure.
      -Sam

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