SPA 9x2 extension to extension call not working (absolutelly mute)

[haguila]

We currently have five SPA942 IP phones, four SPA 922 IP phones and one SPA962 IP phone.

They are all connected to a switch (3C16470), and the switch to the router (3CREVF100-73).

We already have an IP telephony provider.

Outgoing calls from any of these phones work perfectly.

Incoming calls directly to these phones, also work perfectly.

The only problem is with extension-to-extension calls between these phones:

When I call an extension number, the destination extension rings and the call is properly identified on the display, but when the called party picks up the phone, while the connection is active, there is no audio whatsoever.

Looking at the displays of the origin and destination phones, everything is fine, but as I said, neither can hear each other, the line is totally mute, except if one party hits the conf button, then the other one hears the hold music (but never the another party voice is heard).

[nseto]

These phones are all connected to the outside service provider and not to a pbx internally (like spa9000) ?

If that's the case, you are seeing a NAT issue, ask your service provider if they have a session border controller (so the audio can be routed back to the same router ip address, to the proper phone), usually this would then be configured in the outbound proxy setting of the phone.