I have two users at two of our locations that experience one-way audio when calling the other individual. Both of these users are using Cisco IP7945 phones. The person who can hear the audio (let’s call her Shannon), has a phone on the 192.168.4.0/24 subnet and the other user (let’s call him Mike), who is unable to hear Shannon, has a phone on the 192.168.2.0/24 subnet. It only occurs between these two phones. Shannon can call other employees at Mike’s location and they can hear her fine.
Can you provide a sip packet capture of a one-way call, and a call from Shannon to another phone where there is no issue? It’s odd that Shannon doesn’t have an issue with others on Mike’s subnet, so comparing the packets might lead to some clues. Are there any other phones on Shannon’s subnet? If so, are there any issues when Mike calls them? Another thing to look at would be the asterisk output when Shannon calls Mike, and compare it to when Shannon calls someone else. Maybe there’s some odd routing rule in place, though I can’t think of one that would cause this behavior.