I've recently inherited a new network as part of beginning a new job. Historically, my exposure to voice is pretty limited. Without getting into the details of what lead to it, as it's not relevant, after performing a reset on an 8851, the phone grabbed a new IP address DHCP. Later, I found out that, since the new DHCP assignment, the user had been experiencing one-way audio (callers could hear the user, but the user could not hear the callers). There was nothing in the work I'd done that could have caused this, and I soon found out, from others that had been here longer, that this is something that has popped up from time to time. It's apparently so infrequent and intermittent, that it's never been a priority. They have historically resolved the issue by replacing the phone.
The phone and the CUCM are both at the same physical location, with only SVI between them. The phone and all the other phones are on the same VLAN, many on the same switch. There are over 200 phones registered that are not having any issues. I was able to find out that a phone in our IT Lab had the same issue (but was never replaced). I was able to easily resolve the issue by deleting its DHCP lease, and creating a bogus DHCP reservation so the phone would be forced to grab a new IP. Once it had a new IP, everything worked fine. I did the same with the user, and their issue was resolved as well. I then, changed the second bogus DHCP reservation such that the IP Lab (Test) phone would get the user's OLD IP address, and the problem presented again. I understand that one-way audio is almost always caused by routing issues, but with the nature and symptoms of this, it almost seems like there's something cached somewhere that's affecting only certain IPs. The only thing I've experienced, in the past, that was similar was an issue with cached DNS entries needing to be manually cleared, but that was complete broken routing, not something like this.
Anyway, even though it's not at the top of my priority list, I'd still like to understand what's causing this (especially if it's a routing issue that I'm not aware of). I'm still trying to do some research on the side, but has anyone come across a situation like this? I'm also not sure what would be useful, so I just attached screenshots of call stats and diagram from the affected phones.
