we have two UC520 conencted over VPN. when I call from main site to remote site and user in remote site doesn't answer the call, I get dead silence and it seems RTP traffic is not passing through VPN tunnel from CUE. but when I call from remote site to main site, and no body answers the call, I can hear voicemail. I've checked network connectivity from CUE in both sites and they are fine.
What else should I check in the router for CUE RTP troubleshooting?