Rogue AP scanning as a background activity

Rogue AP scanning as a background activity

Each WiFi radio can perform monitoring of radio channels in its operating band while acting as an AP. It does this by briefly switching from AP to monitoring mode. By default, a scan period starts every 300 seconds. Each second a different channel is monitored for 20ms until all channels have been checked.

Monitoring rogue APs                                                                                                  Wireless network monitoring

During heavy AP traffic, it is possible for Spectrum Analysis background scanning to cause lost packets when the radio switches to monitoring. To reduce the probability of lost packets, you can set the CLI ap-bgscan-idle field to delay the switch to monitoring until the AP has been idle for a specified period. This means that heavy AP traffic may slow background scanning.

The following CLI example configures default background rogue scanning operation except that it sets apbgscan-idle to require 100ms of AP inactivity before scanning the next channel.

config wireless-controller wtp-profile edit ourprofile config radio-1 set wids-profile ourwidsprofile set spectrum-analysis enable

end

end

config wireless-controller wids-profile edit ourwidsprofile set ap-scan enable set rogue-scan enable set ap-bgscan-period 300 set ap-bgscan-intv 1 set ap-bgscan-duration 20 set ap-bgscan-idle 100

end


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This entry was posted in Administration Guides, FortiAP, FortiOS 5.6 on by .

About Mike

Michael Pruett, CISSP has a wide range of cyber-security and network engineering expertise. The plethora of vendors that resell hardware but have zero engineering knowledge resulting in the wrong hardware or configuration being deployed is a major pet peeve of Michael's. This site was started in an effort to spread information while providing the option of quality consulting services at a much lower price than Fortinet Professional Services. Owns PacketLlama.Com (Fortinet Hardware Sales) and Office Of The CISO, LLC (Cybersecurity consulting firm).

2 thoughts on “Rogue AP scanning as a background activity

  1. Olof

    Hello, I have an issue where I run an FortiAP U431 (new .11ax AP’s) in dual 5GHz mode. Two radio operating as AP in 5GHz mode, so I can load balance the share. However, on the floor with these AP’s, I am seeing varying receive RSSI on my clients. Could this be due to AP going into rogue scanning mode? Or would that simply just “drop” any signal received.

    Reply
    1. Mike Post author

      I like having both bands to help reduce the problems one may have with range and such. I have never tried to run a single device with both radios on 5GHZ before. Not sure what kind of response you may get from that but considering it is more susceptible to noise it may be a negative experience.

      Reply

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