A typical trouble ticket might sound like "when another extension calls me, I can hear them, but they can not hear me"! Actually, one of my personal faviroites. Over the years I have come to learn that this is usually the result of one of two issues: someone has the wrong default gateway; or port 5004 is being blocked by some firewall in one direction. As we move more and more toward SIP and media streams move away from a dedicated port, this issue is almost always a network configuration error.
So which device has the wrong default gateway? That takes some dedective work. Generally you will telnet into the ShoreTel SG media gateways and check the configurations. Media stream between phones generally do not need an SG switch beyound call setup. The media stream, once the call is setup, is between the two phones. For this reason, you will want to tenet into the phone and "see" the network from the phone's percepective! To do this, you will need to know the ShoreTel methodology and process.
Security on the SG switches and phone, requires that you start the process from the ShoreTel HQ server. There is a specific subdirectory that you need to be in to launch the various utilities. This silent viedo walks you through the process of using one utility, phoneCTL, to telenet into a phone and look around.