Cisco 8540 WLC - 8.5.140.0 - many Access Points in Mode "Monitor"

[ciscoprolin]

Dear All,

we have just noted on our 8540 WLC (8.5.140.0) that about 42 of our approx. 1100 Access Points (mostly 2802I's) have their dual band radio in the radio role "Monitor". We have never manually configured these APs to be in the mode "monitor" which means they do not serve WiFi Clients during that time.

Does anyone know if this is a known issue with RRM or CleanAir ? Also in some areas with bad 2.4 GHz coverage the XOR interface of the APs had been automatically configured to 5 GHz instead of 2.4 GHz with a 2.4 GHz coverage hole as a result.

Any hint and idea is greatly appreciated.

Thanks

[Leo Laohoo]

Is FRA (Flexible Radio Assignment) enabled or not?

[Scott Fella]

Leo is right:) FRA enable can change the roles of the XOR radio.

[ciscoprolin]

Hi,

yes FRA is enabled with low sensitivity, 1 hr. interval and service priority = coverage.

But in our case there was no 2.4 GHz signal available on the entire floor and instead of turning on the 2.4 GHz radio on the XOR interface FRA turned on the Monitor Mode and as a result the clients depending on 2.4 Ghz were no longer able to connect.

FRA is a good idea but only if it does what it's supposed to do which in our case doesn't seem so.

To get the 2.4 Ghz clients back to the wlan we had to manually configure the XOR interface for 2.4 GHz.

Any idea how we could tweak FRA to work as it's supposed to ?

Thanks.

[Leo Laohoo · Accepted solution]

The easiest way is to disable FRA.

[Scott Fella · Accepted solution]

Like Leo mentioned, disable it if it’s not working for you. Like any other feature, it’s a good to have if it works in your environment. The question you have to ask yourself is if a 2.4 radio changes to monitor or 5GHz, do the other AP’s in the area cover the area on 2.4GHz where the AP has changed. There are other values you can change, but that is something you have to change and test. If for example you have a sparse deployment or even an average non high density design, you shouldn’t use FRA if you have devices that are 2.4GHz only or need 2.4GHz beacons seen to actually associate first.

[ciscoprolin]

Hi Scott,

thanks. It looks like that is what I'm gonna have to do. The problem is the areas where the XOR interfaces had been turned to Monitor are not sufficiently provided with 2.4 GHz coverage.

In fact our Ekahau site survey analysis revealed there are large coverage holes in the 2.4 GHz band as a result of FRA.

Thanks guys for your feedback. Perhaps we'll just partially disable FRA on the APs in those areas instead of disabling it altogether on a global level.

Thanks,

Thorsten

[Scott Fella]

No problem. Looks like you did a great job going out an testing. Now you understand your environment better with the data you collected.

[Leo Laohoo · Accepted solution]

I have seen a upgrade of 4800 APs where the entire floor was devoid of any 2.4 Ghz. The reason was there was so much co-channel interference FRA kicked in and all the 4800 were on 5.0 Ghz.
In my opinion, FRA is a great help, however, to get those nasty 2.4 Ghz-only clients working we had to identify the closest AP (in my case, three closest APs) and manually enable 2.4 Ghz.