IVR works for some callers but not others

[Stewart1 (Stewart)]

The Asterisk log should show which codecs were negotiated for each call. You can locate a call that was reported as problematic by timestamp and/or caller ID.

For more detail, you can capture all traffic at the PBX, locate the problematic call, look at whether RTP was coming in to the right port in the right format, and even listen to it if needed. For example, see

Random Dropped Calls on answer 1-3 seconds

As root, run a command like this to capture all SIP and RTP: tcpdump -s 0 -C 100 -W 100 -w rbuf -Z root & This writes a ring buffer of 100 files of 100MB each (rbuf00, rbuf01, …, rbuf99). (Be sure you have 10 GB available disk space.) Assuming that your peak hour is ~200 calls and average call duration is ~2 minutes, you would have ~6 concurrent calls, which is about 50 minutes of captured data. When a dropped call is reported, before the buffer gets overwritten, find the file with the bad c…

Another approach: Temporarily change your IVR settings to allow no retries and route timeouts to a receptionist. If they hear silence, you’ll know the RTP is missing or being misrouted (the problem is unrelated to DTMF or IVR). If they hear garbled or choppy voice, that’s another clue. If the voice is fine (the problem really is related to DTMF), the receptionist can connect the call and you’ll avoid annoying the customer.