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Band Select RSSI vs Mid-RSSI settings

Question regarding configuring the Band Select option on RRM in the 9800 WLC. From what I understand, Band Select will work like this;

client RSSI < Client RSSI WLC setting (Min Value) == no probe response returned

Mid RSSI > client RSSI > (Min  Value) Client RSSI WLC setting == band select disabled

client RSSI > Mid RSSI == band select works as normal

 

So what are the best practices when configuring the Client RSSI WLC setting (Min Value) and the Mid RSSI? What is the behavior like if both are set to the same (i.e. -80 dBm). The reason I ask is I have inherited several WLC 9800s with this configuration (Both set to the same level). We are still using 2702s in the field and I would like to move as many users to the 5GHz as possible.

3 Replies 3

Flavio Miranda
Advisor
Advisor

 

"So what are the best practices when configuring the Client RSSI WLC setting (Min Value) and the Mid RSSI?"

You need to know your RF network pretty well. It will depend a lot. What you can do is take the Site Survey report (If you have one) and look which valeu was considered when the site survey was done. If you dont have one a site survey, you can start for that if you want to be accurated.

 

"What is the behavior like if both are set to the same (i.e. -80 dBm).'

Unpredictable and very unlikely.

 

 

 

The reason I ask is I have inherited several WLC 9800s with this configuration. We are still using 2702s in the field and I would like to move as many users to the 5GHz as possible.

If you can ensure that your clients has 5.0ghz radio, the best approach is disable 2.4 radio on the SSID. 

Thanks for the response. So to elaborate, right now both are set to the same value (-80dBm/-80dBm). This is due to the upgrade from 8540s which did not have the Mid-RSSI setting to the 9800s which do. So it was a legacy setup. I need to know if it is best practice to have a separation between these settings?  When you said it was unpredictable, what did you mean by that?

 

Thanks in advance!

You are saying the your client RSSI is the same as Mid-RSSI, right?

 

Scenario1: Client RSSI (as seen from the show cont d0/d1 | begin RSSI command output) is greater than both Mid RSSI and Acceptable Client RSSI.

 

In your scenario, this condition would not be applied, correct?  Client RSSI must be greater then Mid RSSI and Acceptable Client RSSI.

 


Scenario2: Client RSSI (as seen from show cont d0/d1 | begin RSSI ) lies between Mid-RSSI and Acceptable Client RSSI.

Nor this scenario would be applied.

 

But, as per the WLC docs, we have this two possible scenarios:

=================================

 

Band Select Algorithm

 

The band select algorithm affects clients that use 2.4-GHz band. Initially, when a client sends a probe request to an access point, the corresponding client probe’s Active and Count values (as seen from the band select table) become 1. The algorithm functions based on the following scenarios:

 

Scenario1: Client RSSI (as seen from the show cont d0/d1 | begin RSSI command output) is greater than both Mid RSSI and Acceptable Client RSSI.

Dual-band clients: No 2.4-GHz probe responses are seen at any time; 5-GHz probe responses are seen for all 5-GHz probe requests.

Single-band (2.4-GHz) clients: 2.4-GHz probe responses are seen only after the probe suppression cycle.

After the client’s probe count reaches the configured probe cycle count, the algorithm waits for the Age Out Suppression time and then marks the client probe’s Active value as 0. Then, the algorithm is restarted.

 

 

Scenario2: Client RSSI (as seen from show cont d0/d1 | begin RSSI ) lies between Mid-RSSI and Acceptable Client RSSI.

All 2.4-GHz and 5-GHz probe requests are responded to without any restrictions.

This scenario is similar to the band select disabled.

 

 

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