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High MAC Counters on Metal Roofed Arena - performence problem

Hi all,

I've got problem with WiFi network using MESH.

The WLC is 4402 with 6.0 soft on it. There are 2x 1242 as LAP on conference room, 1x 1242 as RAP and 2x 1242 as MAP.

The network in conference room works really well on both 2,4GHz and 5GHz - clients experience very good performance and no disassociations. That's way I think the problem isn't related to stupid mistake in WLC config.

The problem is on Arena. All bad MAC Counters (FCS, Fails, Retries, Double Retries) on MESH AP are going through the roof. The signal strength is quite good: about -60dBm strength and minimum 25dB SNR. The symptoms suggests IMHO that there are multipath problems. Because of the MESH installation problems are doubled (some packets are lost RAP<->MAP link, and others on MAP<->client link). The effect is that clients associated on RAP are experiencing poor performance and clients associated on MAPs are experiencing abysmal performance. Some pings are going through but half of them have latency over 500ms. The effect is no application can really work; if WWW page loads it takes over 20s, ftp has below 10kb transfer, etc.

I've already tried some things:

- I've disabled 802.11b data rates (1-11Mb/s) to use time window more efficient and leave only data rates with OFDM (which works better with multipath). It help a little bit but not enough.

- I've set custom channel assigment (there are only 3 AP on the field)

- I've tried to optimize custom TX power level. I was hoping that lowering the signal could help limiting multipath problem. The effect was contrary. The signal strength and SNR gone down and the performance was even lower.

- I've red on this forum to lower MTU but not tried yet. Please suggest what could be acceptable low MTU value on 802.11g.

If anyone has other Ideas please let my know.

Best Regards,


Nicolas Darchis
Cisco Employee


my concern is that you said that clients work fine in the conference room on both 2ghz and 5ghz. Does that mean you allow client access to 5ghz ?

If yes that is the problem, The clients are killing the RF in the backhaul band.



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Hi Nicolas,

Thx for the replay. Conference rooms are located deep in the building, and there is no posibility for the MESH APs to here AP or Clients connected in conference room.

best regards,


That's not what I was asking.

I'm asking if you allow clients to connect on 5ghz or not.



Maybe I was not clear enough:

I allow clients do connect on 5GHz only in conference rooms not on Arena where MESH APs are and where the problems appear. I am not allowing clients to connect  on 5GHz on Arena.

Best Regards,


How do you do that restriction ?

if you enabled backhaul client access it's a general setting as far as I know.



The AP on conference room are on local mode so backhaul access doesn't concern them. Backhaul client access is disabled.

best Regards,


Then I would check the 5ghz RF in the arena.

Bad ap/antenna placement maybe ?( close to metallic surface?)

interference ?

this needs onsite analsyis


I've already checked that.

The 5GHz coverage and SNR are good.

Interference are seen but I don't expect it to be main problem. There was still problem with communication when I've done RF site survey when Interference was absent.

Bad antena placement - maybe. I'll try to do tests with other AP and antena placement.

best Regards,


Przemek -

What antenna types/models are being used on the backhauls (5 GHz) and client access (2.4 GHz)?  Are the backhaul antennas omni or directional?  What's the power levels on the APs?  What's the backhaul rate on the APs (24 or 18?).  What data rates are 'required' vs 'supported'?


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