I have an Asus RT-AC88U router at my Mpls office and an RT-AC68U at my Naples office, both running Asus-Merlin Rel 384.17. The Naples Router has an OpenVPN Server Configured. The Mpls Router has an OpenVPN Client Connected to the Naples Router with Create NAT on Tunnel = NO and Inbound Firewall = Allow. The Firewalls on both routers are disabled.
Attached to the router LANs at each location I have a Grandstream UCM6204 IP-PBX systems with Peer SIP Trunks configured connecting the two UCM systems. Each UCM can successfully ping the other UCM.
When I first configure the Peer SIP Trunks on the UCM systems, the connections work fine. After a week or two, the trunks no longer work. The status in the UCM dashboard shows that the SIP Trunks are unreachable. When I do a network trace on each of the UCM systems, they are sending SIP Keep Alive packets to the remote UCM, but the remote UCM does not seem to see these packets. While I have this failure mode, each UCM can still ping the remote UCM.
I’m pulling my hair out trying to figure out why these SIP keep alive packets are being blocked. How can I debug this problem?
Here are the Network Trace Files from both UCM Systems:Grandstream Peer SIP Trunk Problem.zip (292.0 KB)