The VOIP gateway is connected via a LAN connection is connected directly to the Internet and connected directly to the internal network if there is another LAN connection
The VPN connection on the VOIP-Gateway is deactivated.
The VOIP gateway connects to the Internet via another gateway in the network.
The system telephone can be reached from the network of the VOIP gateway via PING.
Make sure that the routing table is entered correctly in the web administration of the telephone system. Then save the routing table in the bootrom. Press 2x on EXIT and then on ‘Save as boot configuration and exit’.
Wait 1 minute and the system telephone should be reachable again via the external VPN connection.