Hello Everyone, I am giving it a try to see how can this forum help me, yeah, my first post... Well, with my installation everything is working fine, two PBX servers, both installed Elastix. One is on public IP address(now on called voip1), and the other (voip4) is having NATing, from its outside IP address, to allow/nat everything inside on UDP 5060, 10000~20000. For VoIP4, also sip_nat.conf is configured: nat=yes externhost=voip4.mydomain.com externrefresh=120 localnet=192.168.1.0/255.255.255.0 Everything with this setup is functioning for both VoIP1 and VoIP4, I have Snom and Aastra phone, connected to both, and they work together through IAX2 Trunking, just fine. But in our office, we have agents all around world, and we just started giving them our Aastra 53i's, so they can connect. I configured the the Aastras just like the ones we have in our offices internally. These agents are to be connected to VoIP4, which is behind NAT. So, as far as the configuration of Aastra is concerned, I had all the configurations done, just like the ones in the office, but instead, put the voip4.mydomain.com as the registrar and outbound server. Story goes on, phones got delivered to the agents, one of them had 3 in his office in Romania, as soon as they turn on the phone, the phone registers just fine, and in the /var/log/asterisk/full, it shows: "chan_sip.c: Peer '50' is now Reachable.", in less than a minute, on some unknown cause, logs show: "chan_sip.c: Peer '50' is now UNREACHABLE!", and in this case, if I have the qualify=yes, the caller during that unreachable period gets the unavailable message. If I put qualify=no, the caller hears ringing, but the actual phone is not ringing at all (even worse). I also tried giving values like 999, 555, 2000, 3000 to qualify, and none seemed to help. For all these extensions, I have canreinvite=no, host=dynamic, nat=yes, with g729 codec allowed only (which the phone supports, and is installed on Elastix servers), type=peer. Out router for all services, is Vyatta V.5. We have other services like our shared folders, and some other working just fine. Even the office phones have no issues. I brought the registration time down to its lowest on the phones, but still, not short enough to catch the "UNREACHABILITY"... I thought the issue is with VoIP4 being under NAT, so moved the agents to VoIP1 (even though that is not what we want), but still, same thing. I have a feeling that there is a misconfiguration, something which somewhere should be exclusively specified for these peers, to make asterisk understand that they are remote, so they it easy with them, or some sort of setting on the phone which I am now aware of? I don't know if I managed to explain everything, but should there be anything missing, please ask me, and I shall provide enough information to clarify. I really need to get over this problem, since they are all on top of my head. Any help is appreciated... Many Thanks, Ali.