Let me preface this by telling you that I have little to no experience with Samsung systems. I'm primarily a network guy but I do wholly manage a Toshiba CTX670 and CTX100 so I'm not completely ignorant when it comes to phone systems.

We had an OfficeServ 7400 installed at one of our locations in Atlanta with ~30 users back in March. There is a small office with 3 users in SC that has VOIP phones connecting to the 7400. Both locations have single T1 lines for all WAN data traffic. The Atlanta site is protected by a firewall and also hosts an Exchange server and Terminal Server for remote users. Internet browsing traffic is pretty light overall. The SC site just has a Linksys router NATing the LAN traffic to the T1.

When the 7400 was installed, we set two static IPs on the system, .42 for the MP40 and .32 for the MGI. Based on the ports given to me from the installer, we setup DNAT policies on the firewall to route inbound WAN traffic on ports 5000, 5003, 5090, 5200, 6000, 6100, and 8080 to .42. Ports 9000, 9001, and 30000-30012 are forwarded to .43. We also have SNAT policies to translate .42 and .43 to the WAN IP for outbound traffic.

At the time, the installer said QoS was not necessary when we asked, so it was not set up. We ended up setting up QoS a short time later due to issues with voice quality. However, since we have no QoS control over the inbound traffic to either location, the QoS did not completely eliminate the quality issues.

This past week, we installed a second WAN connection at the Atlanta location. The above configuration remained identical, except that we have now set the new DSL connection as the default gateway for the firewall, and are using policy-based routing to force only the VOIP traffic across the T1. We did this by specifying any traffic from either .42 or .43, or matching any of the ports listed above should use the T1 IP as the default gateway.

That all seemed to work fine, but the issue now is that occasionally, when the remote IP phone users make a call out, they get connected to the call but there is no voice on either side. Four or five tries later it finally works. Calls incoming to the VOIP phones work fine. Overall, the call quality does seem better than before due to the reduced traffic, but it's still not perfect.

Sorry for the wall of text but it's a very complicated situation. If anyone has any idea what could be causing this new problem it would really help. It did not exist at all prior to installing the DSL.