Interference threshold violated

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Feb 14th, 2008
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I have installed 192 units of Cisco 1131AG AP using wism blade. All up and running now i have some problem. I always get this message alarm in my WCS " interface ' Interference threshold violated". Does this violation is caused because of the Rogue AP's or the infrastructure AP's which are placed nearby.


Based on my understanding if the AP's Within the network if it nearby, WLC wil adjust the power and also the channel so that it doen not overlap more.


Another problem, When a laptop is connected to wireless and i ping to the AD server i have about 1 request time out after 20 or 30 reply. is this normal in wireless connection as i never experiences this prob before..


Can anyone assist me on these issue.


Thank you.

Tass

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Scott Fella Tue, 02/19/2008 - 04:53
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Here is something I found that might help you understand the issues and maybe fix the problem:


WCS Message: AP ''{0}'', interface ''{1}''. Interference threshold violated.


Symptoms: The interference detected on one or more channels is violated.


WCS Severity: Minor.


Probable Causes: There are other 802.11 devices in the same band that are causing interference on channels used by this system.

Recommended Actions If the interference threshold is configured to be too low, you may need to readjust it to a more optimum value.


Investigate interference sources such as other 802.11 devices in the vicinity of this radio interface.


A possible workaround is adding one or more access points to distribute the current load or slightly increasing the threshold of the access point which is displaying this message. To perform this workaround, follow the steps below:


1. Choose Configure > Controllers.

2. Click on any IP address in that column of the All Controllers page.

3. From the left sidebar menu, choose 802.11a or 802.11b/g and then RRM

Thresholds.

4. Adjust the Interference Threshold (%) in the Other Thresholds section.

Field Description

MIB Name

bsnAPInterferenceProfileFailed.

WCS Message

AP ''{0}'', interface ''{1}''. Interference threshold violated.

Symptoms

The interference detected on one or more channels is violated.

WCS Severity

Minor.

Probable Causes

There are other 802.11 devices in the same band that are causing interference on channels used by this system.

Recommended Actions

•If the interference threshold is configured to be too low, you may need to readjust it to a more optimum value.


•Investigate interference sources such as other 802.11 devices in the vicinity of this radio interface.


A possible workaround is adding one or more access points to distribute the current load or slightly increasing the threshold of the access point which is displaying this message. To perform this workaround, follow the steps below:


1. Choose Configure > Controllers.


2. Click on any IP address in that column of the All Controllers page.


3. From the left sidebar menu, choose 802.11a or 802.11b/g and then RRM Thresholds.


4. Adjust the Interference Threshold (%) in the Other Thresholds section.

I also wouldn't worry about dropping pings either, usually on a data WLAN if you drop no more than 8% dont worry as the icmp packets are only ever best effort.

mohanantassp Sun, 02/24/2008 - 17:41
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Below is my ping statistics,


Packets: Sent = 10227, Received = 10167, Lost = 60 (0% loss),


Approximate round trip times in milli-seconds:


Minimum = 1ms, Maximum = 442ms, Average = 3ms



if i refer to this my drop is not more than 8%, which means my Wireless network is still healhty. About The error message from WCS " AP ''{0}'', interface ''{1}''. Interference threshold violated".. .does this interference caused by the Rogue AP or the same infrastructure AP.

Scott Fella Sun, 02/24/2008 - 20:19
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This interference can be caused by both. Looking at your ping times and that you are not talking about any performance issues, I would just ignore this or just change the threshold value.

rmerritt Thu, 02/28/2008 - 10:48
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I have the same issue. In dense environments, it is normal to see this. It has caused some issues with older "B" devices getting very confused. I am looking into changing the algorithm to the 2.4 radio so it will power down lower than the defaults presently allow it.

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