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Wireless capture shows same traffic 2,4 Ghz and 5 Ghz

Mkvts
Level 1
Level 1

Hi,

I recenlty made a wireless capture using a 2800 AP and Wireshark.
I have put one radio in 2,4 Ghz channel 1 and 1 radio in 5 Ghz channel 44.

From what I can see now in the trace file after decryption is that I see the same messages (UDP) on channel 1 and channel 44.
On exact the same time in the air, the same messages between client / server.

On the devices I cannot see these message leaving the device (twice on 2,4 and 5 Ghz).

Is this a known thing? Did i mis configure?

I cannot share this file.

1 Accepted Solution

Accepted Solutions

Rich R
VIP
VIP

You definitely won't have simultaneous dual band transmission from a 2800!  And in any case this is the PDA we're talking about sending the packets.  So whatever you're seeing is something to do with the way it's been captured - quite possibly a bug in the capture.  If the PDA didn't send it on both channels then it's technically impossible for it to have been received on both channels.

So make sure the 2800 software version is up to date in case it is a known bug which has been fixed.  Refer to TAC recommended releases below.

What WLC model and software version are you using currently?

View solution in original post

5 Replies 5

JPavonM
VIP
VIP

Qualcomm have some chipset that connect on dual-band to transmit, they call this Dual Band Simultaneous Transmission (DBS), something that is about to be implemented on Wi-Fi7 standard.
https://www.qualcomm.com/products/technology/wi-fi/fastconnect
https://www.qualcomm.com/news/onq/2020/06/mobile-wi-fi-6-performance-4-stream-dbs
https://www.qualcomm.com/news/onq/2020/05/qualcomm-fastconnect-raising-bar-mobile-connectivity-advanced-wi-fi-6e-and

An example of this is the "Qualcomm WCN685x Wi-Fi 6E Dual Band Simultaneous (DBS) Network Adapter"

Mkvts
Level 1
Level 1

@JPavonM thank you for your response, I'll check the chipset but I expect this is a very cheap / old one.

The traffic is comming from a small PDA which has a Linux shell on it.

From what I can also see in the trace file is that sometimes the PDA is sending out packets (UDP) and resending them using different bitrates. If I have any other information I'll update this

Rich R
VIP
VIP

You definitely won't have simultaneous dual band transmission from a 2800!  And in any case this is the PDA we're talking about sending the packets.  So whatever you're seeing is something to do with the way it's been captured - quite possibly a bug in the capture.  If the PDA didn't send it on both channels then it's technically impossible for it to have been received on both channels.

So make sure the 2800 software version is up to date in case it is a known bug which has been fixed.  Refer to TAC recommended releases below.

What WLC model and software version are you using currently?

JPavonM
VIP
VIP

As Rich mentioned this could be a capture issue, which software and hardware are you using to make the OTA capture? 

Mkvts
Level 1
Level 1

Hi,

Getting back on this, yes it was a capture issue. I have no idea what happend but did another capture and did not show the messages in the air over 2,4 Ghz and 5 Ghz.

For everyone that has this issue to. Restart you capture. I've also rebooted the sniffer AP just to be sure.

Thanks for the help  

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