Anomaly on Packet Capture

AndrewSotiris

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Hello,

As part of a diagnostic test, I ran a packet capture between a Yealink T73U and the SBC it reports to. To maximize the collected data, the capture was run on the SBC and recorded packets between just the SBC and the IP Phone. To run this test, I used the following procedure:

1. SSH into SBC and prepare command to run packet capture sudo tcpdump -i any host [IP ADDRESS OF PHONE] -w /tmp/sbc_trace.pcap -C 50 -W 5
2. Impersonate extension 4132 in the 3CX web console
3. Start TCP Dump
4. Trigger call from user's T73U to me
5. Answer call
6. Wait five minutes and end call
7. Kill tcpdump process with ctrl+c

I analyzed the Packet Capture with Wireshark and was able to find the test call. Everything on the test call looks fine, but there's a second call recorded in the capture that started midway through the test call. The call goes from 4132 to 4132 and was still in progress when the capture ended. Nothing in the call logs, event logs, or activity logs corroborates this call existing. Any idea what this "ghost call" is?

1787806611932.png
 
Hello Andrew,

The call you are seeing is the CSTA communication of the phone with the PBX exchanging information. It's perfectly normal traffic.
 
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