We have a user that connects to our Mitel 250 system via an external IP that is NAT'd to the phone system. This has been working fine for years up until the last couple of weeks. Now when he uses the phone, there is a 10 second delay on his side before he can hear anyone on the other end. After that delay, the phone works fine until you hang up and use it again. At first I assumed there was an issue with his network since he had just recently replaced his modem and router and he wasn't having the issue prior. We have setup IP phones at two other external networks though and they experience the same issue. I've checked with our network vendor and obviously the ports are open for this external IP or the calls wouldn't work at all. I've also asked to make sure there is no DPI being performed and they are saying there isn't. Any ideas on what the issue could be? I'm at a loss for what could have caused this change in the last couple weeks.
