I've been trying to troubleshoot a setup that was working at one point and since stopped. Client has a SV8100 with a remote phone that connects over VPN and is working. They also have a few remote users that have u-Mobility (firewall is a Cisco ASA with the following ports forwarded to phone system: udp/5070,udp/5080-1,udp/10020-10051,udp/10052-10083,udp/15061.

Android phones seem to work fine when offsite, but iPhones seem to register without and issue and can make calls, but there isn't any audio on the call. Doing a capture at the firewall I see the inbound audio from the iPhone being forwarded to the phone system but users in the office never hear anything. I don't believe there is any ringback either on the calls to the iPhone. I'm trying to setup a side by side test of an Android device and an iPhone but looking for ideas that i might have missed.

This was working properly initially but it was reported that it stopped after the internal addresses on the LAN changed.

That is UDP blocking somewhere. I am assuming the iPhone is on a VPN. If that is when the issue started you already know where to start looking.

We've tried the iPhone both on VPN and off, same issue. We're only able to get it to work when the iPhone is connected behind a router that has SIP ALG enabled (it is disabled on the firewall in front of the phone system). The strange thing is when the changes were made on the network the phone system wasn't touched (a 2nd vlan was added, phone system ip and vlan remained the same). At that point it would work if the iPhone was on a wireless network that was on the same subnet as the phone system, but not on another subnet that is local to the site. After changing the ip of the phone system the issue remains, but iPhones don't work at all now.