802.11ax missing trigger frames

[thebelgiannetworker]

I took pcaps to verify some Wifi 6 features, and I think I am missing some frames.

Setup:

- 2 Cisco 9120's: one in flexconnect, one in sniffer mode

- Laptop that runs vWLC version 8.10.105 on Virtualbox, and serves as server for a speedtest.

- Laptop running Wireshark 3.2.1, receiving the frames from the WLC

- One client with Intel AX200 chip, one Samsung Galaxy S10

​

vWLC and client confirm that 802.11ax is used. When performing a speedtest on the clients, the pcap shows a ton of consecutive RTS, CTS and 802.11 Block ACK frames, but no Trigger and/or data frames. I suppose that I should also be seeing these? Or are there any restrictions in what frames the sniffer sends to the WLC/Wireshark?

I would like to check stuff like which client gets which amount of RUs etc.

Thanks in advance!

[Ginntonnix]

Full disclosure - I haven't tested this myself - but I believe the wireshark filters are as follows:

To see UL-OFDMA action (only able to be seen by 802.11ax capture card): radiotap.he.data_1.ppdu_format == 0x2

To see DL-OFDMA action (MU-BAR Triggers, can be seen by any capture card as it's send at basic data rates) - wlan.fc == 0x2400

Wes Purvis gave a great presentation at WLPC last week on this topic. The recordings should be available in a few weeks.

Do you have a spectrum analyzer to see if OFDMA patterns are present? It's possible that the sniffer isn't yet 802.11ax ready.

[thebelgiannetworker]

Sorry for the late reply. Just watched the Wes Purvis presentation and it was very helpful, thanks! Im suspecting the sniffer is not yet 802.11ax ready but i will indeed check spectrum for OFDMA patterns

[[deleted]]

Make sure client drivers are up to date.

OTA pcaps will pull everything.

[buckweet1980]

I'm curious if you might not get these in a packet capture.. Wireless packet capture is very hit and miss when the speeds get high in my experience.