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Rtp dynamic payload type 123


We have a problem about RTP dynamic payload type 123. If you know, please explain when cisco gateways are nagotiation between non-cisco media gateways. When we look at rtp packets, Wireshark tag this packets malformed. Is there a way Can we disable between gateways are nagotiation with dynamic payload type 123.

i found only below info about rtp dynamic payload type 123 that is used for indicating Cisco CAS information.

RTP Payload Value

RTP Payload Definition


Indicates Cisco CAS information.




Rtp dynamic payload type 123

What is your hardware?

Do you have already see this doc?

Enable RTP Signaling on AS5350 and AS5400

In order to prevent errors caused by RTP packets of payload type “123” on Cisco AS5350 and AS5400 series platforms, RTP signal processing is disabled by default. Under some circumstances, packets of this type can cause an invalid memory address error in AS5350 and AS5400 series platforms, potentially crashing the devices.

On these models, you can enable RTP signal processing using the voice-fastpath voice-rtp-signalling enable hidden configuration command. However, before you enable RTP signal processing, prepare the platform to handle RTP packets of payload type “123” by enabling T-CCS.

After you prepare the platform, you can use these commands in order to enable or disable RTP signal processing.

  • In order to enable RTP signal processing, use this command:

    Router(config)#voice-fastpath voice-rtp-signalling enable
  • In order to disable RTP signal processing, use this command:
    Router(config)#no voice-fastpath voice-rtp-signalling enable
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Rtp dynamic payload type 123

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