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Off Channel Scanning Defer Best Practices

I work in an environment where it is QoS-centric.  I was reading up on the "Off Channel Scanning Defer" setting on the Advanced tab of the WLANs configuration.  By default, the Scan Defer Priority is set for 4,5,6 and the Scan Defer time is set to 100ms.  I read in another article that 0-3 should be activated if the WLAN is used for non-priority traffic, such as web browsing.  There are no wireless IP phones in my environment.  On our main WLAN , which is used for general traffic, QoS is set to Bronze.  Wouldn't it make sense to to enable 0-3 and also tweak the Scan Defer time to improve performance on said WLAN?

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VIP Mentor

There are no wireless IP phones in my environment.  On our main WLAN , which is used for general traffic, QoS is set to Bronze.  Wouldn't it make sense to to enable 0-3 and also tweak the Scan Defer time to improve performance on said WLAN?

QoS profile set to Bronze, effectively you are treating all wireless traffic same & all get DSCP=0 when it goes from WLC to wired side of your network. (effectively no QoS differentiation for your wireless traffic). Refer this for details

http://mrncciew.com/2012/12/02/understanding-wireless-qos-part-3/

Off Channel scan defer is used when AP has higher priority (voice,video) traffic to transmit, it can defer going off channel to scan RF & deliver those important traffic to clients. I would not enable this for any lower 0-3 priority traffic as it will result most of the time your radio will defer off channel scanning.

So leave it to default & think about configure QoS profile Platinum for your SSID if that carry any delay sensitive traffic.

 

HTH

Rasika

**** Pls rate all useful responses ****

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VIP Mentor

There are no wireless IP phones in my environment.  On our main WLAN , which is used for general traffic, QoS is set to Bronze.  Wouldn't it make sense to to enable 0-3 and also tweak the Scan Defer time to improve performance on said WLAN?

QoS profile set to Bronze, effectively you are treating all wireless traffic same & all get DSCP=0 when it goes from WLC to wired side of your network. (effectively no QoS differentiation for your wireless traffic). Refer this for details

http://mrncciew.com/2012/12/02/understanding-wireless-qos-part-3/

Off Channel scan defer is used when AP has higher priority (voice,video) traffic to transmit, it can defer going off channel to scan RF & deliver those important traffic to clients. I would not enable this for any lower 0-3 priority traffic as it will result most of the time your radio will defer off channel scanning.

So leave it to default & think about configure QoS profile Platinum for your SSID if that carry any delay sensitive traffic.

 

HTH

Rasika

**** Pls rate all useful responses ****

View solution in original post

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Cisco Employee

Please refer to the similar post in community forum-

https://supportforums.cisco.com/discussion/11847136/what-purpose-channel-scanning-defer-priority

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