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New Member

Dynamic Channel Assignment Question

I have a WLC 4400, and I have discovered that some areas, the access points are on the same channel. For example the floor have four access points, and the access points are working in this channels:

AP01=channel 01

AP02=channel 11

AP03=channel 11

AP04=channel 11

If Dynamic Channel Assignment is enable in the controller, Why the access points are on the same channel?

The access points are near each other.

WLC4400 System version 6.0

Any suggestion?

Is better manual configuration?

8 REPLIES
Cisco Employee

Re: Dynamic Channel Assignment Question

RRM works in such a way that, if required the DCA will change the channel to overcome the interference.. if not required then it will not change the channel. here is the Doc..

http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a008072c759.shtml

Lemme know if this answered your question

Regards
Surendra

Cisco Employee

Re: Dynamic Channel Assignment Question

To add to Surendra's reply, it is not a problem for 2 APs to be on the same channel if they don't have a heavy load or if they are too far away from each other or if all other channels are jammed by rogues.

Check out in the "show run-config" at what signal strength your APs hear each other. If they hear the other APs at a bad signal then you have your explanation.

Nicolas

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New Member

Re: Dynamic Channel Assignment Question

Thanks Nicolas,

I have this question, what is the recommended  value received of signal strength of a neighbor  AP??

Cisco Employee

Re: Dynamic Channel Assignment Question

Well, if you see another AP on the same channel heard louder (=number closer to 0) than -70dbm that's where you start to worry. That's also usually when the WLC algorithm kicks in and reduces power. So you can have 3 APs ( in b/g channel 1,6,11) at -60dbm, that's fine, but as soon as a 4th AP is loud like that then the WLC will lower power.

On the other hand, if there is no AP (even on different channel) that is louder than -75 I would (not a hard rule), roaming will become maybe a bit difficult.

Nicolas

New Member

Re: Dynamic Channel Assignment Question

Thanks Nicolas,

The last question,

With that CLI command in the WLC, I can see the power of a neighbor ap?

Cisco Employee

Re: Dynamic Channel Assignment Question

show ap auto-rf 802.11b

replace with "802.11a" for 5ghz

The complete list is present in a "show run-config"

Nicolas

====

Don't forget to rate answers that you find useful

New Member

Re: Dynamic Channel Assignment Question

Hi Nicolas I have this situation:

AP Name.......................................... AP22
MAC Address...................................... 00:1d:a1:zz:yy:xx
  Radio Type..................................... RADIO_TYPE_80211b/g

  Radar Information
      Recommended Best Channel..................... 1

  Nearby APs
    AP AP53 slot 0..................  -67 dBm on   1 ()
    AP AP12 slot 0..................  -57 dBm on   6 ()

The AP22 is working in the channel 1. ButI have another AP, in the same channel 1, this is normal operation?

When a Nerby AP is considered away? when the dbm is -70, -71, -72 or -75, -74, -73 ??

Thanks

Cisco Employee

Re: Dynamic Channel Assignment Question

The general answer is "the algorithm is more often right than you" :-)

Here we can see that there an AP on channel 6 that is much closer, so the only alternative would have been channel 11.

Imagine that there is a rogue AP on channel 11 that is sending lots of crap. Or worse, an AP on channel 9 that is not creating load on channel 11 but interference (channel 9 overlapping 50% on channel 11), that makes channel 11 unusable.

If you activated "cisco ap load" in the algorithm, then the WLC also thinks it's ok for 2 of your APs to share a channel if they are not transmitting a lot.

Regards,

Nicolas

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