I have little snag in completing the deployment of our new phone system. We have 7 phones deployed and working well on our network. I have a problem with 2 other phones (grandstream GXP2120s) connecting, though. One is set at a far end of the complex behind a small router (WRT54GL) and the other one is connected in the tech room which is behind another small router (same kind). Issue 1: I have the other 7 phones all set with static IPs. They find the 3CX server and are in use and make great sounding calls. These 2 phones wouldn't register this way. The only way they would register was to set to DHCP (giving them a 192.168.1.x address issued from these small wifi routers and not one of the static IPs [10.0.0.x] like the rest). I feel like this is a basic networking problem that I've solved many times, but for some reason am not figuring it out right away with these phones. Issue 2: These two phones are also only sending audio (receiving extension can hear the audio), but aren't receiving any audio. I read something about having to set the STUN server in the Grandstream GUI, but am unclear about that. Also think it might be something to do with NAT traversal, but haven't found great documentation about that. Any help and suggestions are appreciated. Thanks.