I am having some trouble with a UC520/CUE with a SIP Trunk Provider.
The scenario is that we have the UC520 on our LAN with its F0/0 WAN port directly connected to a DMZ, with a public IP Address on the internet, and we have inbound/outbound calls via a UK SIP Provider. Inbound and Outbound calls are ok (to a Cisco Phone running SCCP).
However, when an inbound call is fowarded to the CUE module over the CUE SIP trunk, the caller hears the Voicemail greeting, can press keys so DTMF works, the media streams "seem" to be up, but I get no voice packets received by the CUE. The caler thinks they are leaving a Voice Message, but the CUE never receives the audio.
I have diabled H.450.2/3 etc and added the "allow connections sip to sip" to try and purely hairpin the call via the UC520 to the CUE, avoiding any media renegotiation/NAT issues, but no luck.
I also have an H.323 trunk to anothe CME, and if a call comes in over the H.323 trunk, and is forwarded to the CUE, it's fine, but its over an internal connection/GRE tunnel so no NAT etc is involved.
Anyone have any ideas?