Controller Based WLANs

Environment : General

Here are some best practices for RF optimization in the controller based solution that have been found to work quite well on quite a few occasions.

First of all, optimize the amount of traffic in the air:

• Drop broadcast and multicast (watch out, if on a sw version prior to 6.3, you'll need to enable broadcast-filter arp in the stateful firewall)
• Disable the lower speed rates. Depending on the AP density, I like to start on 12-18 Mbps
• Use as few SSIDs as possible. Generally, one WPA2 Enterprise SSID and one Open SSID are more than enough.
• Enable Dynamic Multicast Optimization (and raise the threshold to, at least 20). Even if you're not aware, there's usually MCAST traffic around.
• Enable Broadcast-Multicast optimization in the L3 interfaces as well.
• Use small vlans + VLAN pooling. I like using /24 vlans and then group them into named pools.
• Enable EAPOL optimization.
• Enable Airgroup. This will convert mDNS traffic into unicast, decreasing the amount of traffic in the air and saving some precious battery on your mobile devices.

After that, make sure you make the most of that airtime you're giving the users:

• Enable Airtime Fairness
• Enable Band steering (not needed if you're using Client Match [requires version 6.3]). There is way more spectrum available in 5GHz, lets use it!
• Enable Client Match. This is a no brainer, just do it.
• Enable WMM
• For those applications that don't handle WMM so well, configure your roles so that corporate multimedia traffic is prioritized.
• If you want to make sure your corporate traffic always has priority over guest traffic, you can reserve some airtime in the QoS section of your AP Group

With that kind of tuning, your wireless network should already be doing quite well, but there are a couple of things you might want to do if you need additional fine tuning:

• Make sure your APs don't use too much or too little power compared to client devices. Min power set to 12dBm and max to 18dBm usually works quite well. But don't take this as one-size-fits-all some scenarios need full 20 dBm in the APs and some can do with a bit less. You can fine tune that using the "show arm rf-summary" command and seeing how the APs are seeing each other.
• On very dense deployments, you might want to turn off (convert to AM or SM) some radios, specially in the 2,4GHz band. This will help reduce co-channel interference.
• Advertise 802.11d/h.
• Disable 802.11k. Some Windows clients don't take it too well.
• If you have some overlap between your Aruba WLAN and another WLAN present on-site. fdb-update on assoc (in your virtual aps) will definitely improve roaming between both networks.