AP Channel selection with no Radio Resource Provision
I know if I enable Radio Resource Provision under FortiAP profiles, the APs will scan the frequency range and select the channel with less interference between the other APs, this is well documented in Deploying Wireless Network Guide.
But what happens if this feature is not enabled? I have several APs working with this feature disabled:
The APs have selected a channel, some on channel 1, some on channel 11... Do you know what the criteria or algorithm is for this channel selection?
My understanding is that when an AP initially boots up , it automatically does a scan of the environment and based off of that, selects a channel (unless the channel was manually configured). If the "radio resource provision" feature is enabled, it will continue to do this type of scan periodically (by default, every 30 mins). You can adjust the frequency of how often this scan is done via the CLI:
...I have enabled this feature for my FortiAPs and they are changing the channels very often, but I don't know if they change channels always they find bettter channels or only if they find better channels and have no associated clients.
If DARRP is enabled, then i believe even if clients are connected, the AP will change channels at the set interval (would be awesome if someone from fortinet could confirm but I'm pretty sure this is right). This is why it is important to change the frequency of this scan to some time period that is normally quiet (for example, 3AM).
>>But what happens if this feature is not enabled?
If the DARRP is not selected the AP hooks on to one channel forever with which it came up during bootup process. There is no channel optimization algorithm running in background that calculates the interference & suggests the AP's to move to better channel if available.