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Cisco Bug: CSCvv35758 - Excessive RTS from AP leading to High Channel Utilization

Last Modified

Sep 01, 2020

Products (1)

  • Cisco Aironet 1850 Series Access Points

Known Affected Releases


Description (partial)

APs transmitting excessive amount of RTS as confirmed with wireless packet captures, which seems to cause High Channel Utilization due to AP reserving the channel even when no data frames are transmitted after RTS/CTS exchange.

Packet captures show bursts of RTS/CTS, where more than 50% of the frames on a BSSID could be RTS/CTS, even when data frames are less than 5%.

- Confirmed on 3800 series AP on a C9800 running 16.12.3ES11.
- Confirmed in 5GHz band.
- This is randomly affecting different APs at different periods, regardless of the 5GHz channel. RTS/CTS bursts simply stop, and channel utilization lowers.
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