We have signed up with a Microsoft certified Lync SIP Trunk provider. The issue we are having is the SIP packets sent from Lync contain the internal IP address of the Lync server not the routable WAN IP address and calls fail as a result.
Our setup is a Lync 2010 Standard server with co-located mediation server. We are using a Fortigate 80c Router / Firewall which is doing NAT / PAT for Lync. We have implemented SIP ALG on the Fortigate.
Our setup has worked but is intermittently dropping out the calls, our provider says this is due to the information Lync is sending.
Can you please advise how to change the SIP packet information to send the WAN IP and not the internal.
Packet traces attached (images anyway, couldn't upload the Wireshark capture)