Cisco WLC8540 and RRM

[trondaker]

Hi,

We have a 8540 running 8.3.133 and around 3000 18xxi APs. Looking at some of our locations reporting poor performance, i see several of the APs on the same channel as eachother, or on the same channel as 3-4 rogues, at quite high RSSI (-60ish dBm). Why on earth would the controller place them here and not move them when sensing the rogues/neighbors? I read on the documentation that RRM prefers non-dfs channels first, then 52-64, and then 100->. We have uni-2 extended channels enabled, so we have lots of channels to chose from, but it almost never places an AP above channel 64. 

The RRM options enabled for 5 GHz are:

Avoid Foreign AP interference

Avoid non-802.11a noise

Avoid Persistent Non-WiFi Interference

DCA sensitivity is set to Medium, and channel width is 20. Channels enabled: 36, 40, 44, 48, 52, 56, 60, 64, 100, 104, 108, 112, 116, 132, 136, 140

[Flavio Miranda]

Hi

 Thats a good question. My assumption bit that RRM fail. However, I'd change the DCA to high and make sure event driven is enable.

 Check channel utilization, If not high then the low  performance my be not due CCI. Determine performance issue sometime is tricky and not always is CCI. 

-If I helped you somehow, please, rate it as useful.-

[trondaker]

Thanks for your reply Flavio! Sorry, forgot to include the EDRRM-settings:

EDRRM Enabled

Sensitivity Medium

Rogue Contribution Enabled

Rogue Duty-cycle 80 <- Is it because this is set so high that RRM ignores rogues on same channel?

As you point out, the duty cycles on these locations arent that high - so might not be the cause, i just like the channels to be clean :)

[Flavio Miranda]

Depending on how many rogues the wlc see it may have no alternative.  Although I think RRM is far for perfect I prefer still trust it rather then set channel manually.

 I think the cornerstone is Channel Utilization. If not too high, then, look somewhere else.

-If I helped you somehow, please, rate it as useful.-

[Freerk Terpstra]

My experience is that, as long as you restrict the Tx powers based on your RF design, the algorithm does a decent job. RRM relies on NDP messages and information gathered during the off-channel scanning, did you change any of these parameters?

You aren't using any RF-profiles which might contain a limited set of channels? If this isn't the case, please share the RF related graphs (for a few access points) listed under "Monitor -> Access Points -> Radios -> 802.11a/n/ac -> Detail" so we can get a closer look at your RF. Another thing to check are radar/DFS messages within the trap logs of the WLC and/or Prime.

Last but not least, be aware that TAC does not recommend using any 8.3.13xx release due to a S1 bug.

Please rate useful posts... :-)

[aapassociateswifi]

Hi, we have come across this.  I found that RRM isn't working properly.  The reason is that, randomly, APs will stop sending NDP frames to each other so RRM doesn't have a true RF picture and either doesn't work correctly or makes incorrect decisions.  TAC hasn't provided either a fix or a root cause nor a proxy for when the issue occurs on an AP so we can audit the network ongoing.  I'm going to open up another discussion on this in hopes of generating some community ideas.