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Community Member

Utilizing 1,4,6,9,11 vs only 1,6,11 ; which better?

Hi experts, We must deploy upto 8 ssid in the same area due to commercial reason. With only one big infrastructure wlc8500+500ap. With 8 ssid simutanously, should separate into TWO group of 4+4 (AP group)? Due to 4-5 ssid/ap limitation (too much beacon if a ap broadcast more that 4-5 ssid) If so, is it better to let 1st group to use 1,6,11 and 2nd group for 4,9 (forcing by RF profile) vs 1st & 2nd group for only 1,6,11 In term of interference, duty cylce etc. Which on is better? Thank you & Br Nipat CCIE#29422
5 REPLIES
Hall of Fame Super Gold

Leave the Dynamic Channel

Leave the Dynamic Channel Assignment (DCA) and Tx Power Control (TPC) set to auto.

Cisco Employee

Hi, It's always good to use

Hi,

 

It's always good to use non over lapping channels 1,6 and 11. As you are using a controller based set up You need not have to assign the channels manually, the WLC will assign the non overlapping channels to the APs. you can broadcast maximum of 16 SSIDs per radio, so it doesn't matter if you use the 4 to 5 SSID per AP or radio.

Regards

Salma

Community Member

Hi salma, I got a clue

Hi salma,

 

I got a clue (testing) classical rule of thump of minimisation of SSID# concept.

http://www.revolutionwifi.net/2010/10/limit-ssids-data-rates-to-maintain.html

 

Here is an example. Assuming 6 SSIDs per-AP, 100ms TBTT, and 3 co-channel APs in the same area (within signal range to induce CCA medium busy backoff amongst each other):

Note 2013-08-16: This assumes a 180 byte beacon frame, which is probably too low for modern WLANs which have added many features that result in more Information Elements. For example, I typically measure beacons at around 370-400 bytes today. 802.11u and Hotspot 2.0 capabilities will increase this further. So, these calculations on bandwidth utilization are probably about half of what they are today. Double these numbers :) I'll try to post another blog updating these numbers accordingly.
 
   Beacon Data Rate     Resulting Channel Bandwidth Utilization
   1 Mbps               25.92%
   2 Mbps               12.96%
   5.5 Mbps             4.71%
   11 Mbps              2.36%
   6 Mbps (802.11a/g)   4.32%
   12 Mbps (802.11a/g)  2.16%
 
Same network example, now with only 3 SSIDs per-AP:
 
   Beacon Data Rate     Resulting Channel Bandwidth Utilization
   1 Mbps               12.96%
   2 Mbps               6.48%
   5.5 Mbps             2.36%
   11 Mbps              1.18%
   6 Mbps (802.11a/g)   2.16%
   12 Mbps (802.11a/g)  1.08%

 

That's fine to let WLC calculate their channel DCA, I'm totally agree!!!

Then, should I go whether all AP with 8-SSID broadcast OR 2 AP group (4 SSID each)?

 

Thanks

 

 

 

Hall of Fame Super Silver

Like everyone stated... use

Like everyone stated... use only 1,6,11.  As far as 8 SSID's, if you don't need to broadcast all SSID's on each AP, then don't.  Create as many AP groups as you need to limit the number of SSID's that is available on a given AP.  You can create more than two AP Groups to also allow you to define different RF Profiles for certain areas.  There are many tweaks you can do, but you need to understand the environment in general.  RF profiles can be used when you have various building types, density of access points, etc.  Also, DCA should be set to 24hours after the environment has settled.  Set your max tx and min tx also... all of these can help size the RF to each environment.

Scott

-Scott
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VIP Purple

Never use anything other than

Never use anything other than 1,6,11. It will worsen your interference within your network as well as with outside your network. (eg CH4 will interfere with both CH1 & CH6, CH9 will interfere with CH6 & CH11).

As 2.4GHz band is already congested, I would rather prefer 5GHz over 2.4GHz (using band select). Leave 2.4GHz only for devices that does not support 5GHz.

5GHz is the way to go (802.11ac supports only in this band)

 

HTH

Rasika

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