I've got a CIX670 with a MIPU24 (software on the MIPU and CIX updated to current around July 2015) that I'm am trying to connect to with a Multitech MultiVOIP MVP-130FXS.

I have the MVP-130FXS (with an analog phone attached) setup as a SIP-type station (I have 8 free IP end-point port licenses). I have the MIPU and MVP-130FXS configured for G711u.

I can dial the MVP-130FXS station number from another station and the MVP-130FXS station rings, picking up the call connects, but there is no audio. Same happens in the opposite direction. Dialing from the MVP-130FXS station I can send digits (out of band with RFC2833 configured) and dial out with LCR and call my cell phone. Never any audio. So the SIP connection seems to be working but not the RTP part.

Wireshark confirms that the MVP-130FXS is registering via SIP (the IPT table of the MIPU also shows the IP address of the MVP-130FXS station once it registers). Wireshark also shows the call being setup (and eventually terminated once one station hangs up) via SIP, but only shows RTP packets being sent FROM the MVP-130FXS to the MIPU. The MIPU is not sending any RTP packets (nor does it seem to be receiving them; I have no audio, not even one way audio). I am mirroring both the MIPU and MVP-130FXS switch ports to the port I am running Wireshark on; so I'm sure I'm seeing everything coming from both devices.

I've configured packetization time on both the MIPU and MVP-130FXS to 20ms for G711u.

I've captured the RTP stream from the MVP-130FXS with Wireshark and played back the audio... that stream is good. I just can't figure out why the MIPU is not sending RTP packets back to the MVP-130FXS.

There is also a MIPU16 in the system that is connected via SIP (VM-SIP) to a Toshiba LUCA voicemail system. It works fine.

Anyone have any ideas?

Thanks.