SPAN Issue for Capturing RTP packets

Unanswered Question
Dec 19th, 2007

Hi,

we are implementing a VoIP Recorder (which has not successfully captured both ends of the conversation, only one-way). The actual VoIP call is a two-way conversation - no issues in this regard.

To simply the situation, I connected Wireshark to a 3560 switch port and configured it to monitor one specific port, in both directions (default setting but I specified "both" regardless). The specific port contains an IP phone.

Wireshark does not sniff RTP packets in both directions, only one. When we change which phone initiates the call, the same scenario occurs.

This is a local SPAN, the sniffer and both IP phone connected to the exact same switch, the exact same VLANs. I even tried VSPAN but still get the same scenario. BTW, these IP phones are non-Cisco and we are investigating with the manufacturer as well as to why RTP packets (which are confirmed traversing in both directions are only cpatured in one).

Any ideas would be appreciated.

Thanks,

I have this problem too.
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