In a Mist WiFi deployment, you may see client events that say something like 802.11 Auth Denied due to BandSteer
This sounds like a problem right? Auth denied? That can’t be good…
Well, it might be misleading, but it’s not really a problem. What does it mean? It comes down to Band Steering.
Many WiFi systems support both 2.5GHz and 5GHz. In general, we prefer to use 5GHz when possible, as this is where the higher speeds are reached. So when a client connects to 2.4GHz, Mist will try to steer them to the 5GHz band.
This is not specific to Mist either. Most, if not all WiFi systems, will support band steering. It’s usually a configurable option that you can turn on or off.
However, the AP can’t tell the client which band to connect to. This is up to the client to decide. It can only try to influence which band is used.
Each WiFi vendor may have different ways they implement this. Mist will cause the 802.11 authentication to fail on 2.4GHz, but succeed on 5GHz. And this is the meaning behind the ‘error’ we see.
So when you see this in your Mist logs, you can be comfortable that everything is working as expected.