PSTN --- Nortel Meridien PBX --QSIG--- Cisco 3845 ---- Checkpoint FW (Allow IP any any) ---- LAN --- IP Phone
When IP Phone A makes a call to a mobile phone @ PSTN, the mobile phone rings, but there is no ringback tone at the IP Phone. When the call is answered, the mobile phone can hear IP phone, but IP phone cannot hear mobile phone.
We verified IP connectivity between the Cisco 3845 and the IP Phone:
- Logon to phone's web page, at stream 1, it is connected to the 3845's loopback address, and the send/recv packet counters are increasing
- Sniff packets at Checkpoint FW, at both interface I can see rtp packets going to both directions.
- Did a debug voip rtp at the 3845, we can see rtp packets sent and recv'd.
You can see in the show call active voice brief this:
-25 doesn't appear to be changing on the input dB, which is what we're interested in. This points towards a problem on the PBX.
As well, if it's intermittent for PBX phones and constant for PSTN phones, this points towards the PBX as well. We are going to connect to the PBX exactly the same for both scenarios, and this sounds like the PBX should be investigated further.
This can be proven with a PCM capture, but a PCM capture requires a TAC case.
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