Hi All, we have a problem with SIP extensions on the Mitel 3300. We can make calls from the SIP extension into any office extension inside our network and it works fine. When we call a teleworker or other SIP extension that is residing outside our network the caller gets ringtone but cannot hear the remote party when they answer. If any extension rings the SIP extension the SIP extension rings. When you off hook the SIP handset you cannot hear the calling party. In fact it seems as if you have lifted the receiver and held down the hook. The calling party continues to hear ring tone until the call times out. We suspect that it is a router/firewall issue but are frankly scratching our heads as the Mitel documentation does not clearly explain the routing.
We would appreciate any advice or a definative list of the ports that are required to be open when using SIP extensions
