I've been having this problem for some time, and I can't find a solution or fix it, and now I'm wondering if what I'm trying to achieve is possible. So at our office we use a 2011iLS-IN router, and we have a VPN L2TP, ipsec connection set up. We also have a Samsung OfficeServ 7200 PBX server, connected to the router, for our phone system, that allows us to have IP telephones connected to it, from a remote location, for example, at homes of our employees. The IP telephone connects trough the public IP of our network at the office, and so does the VPN connection.
The problem occurs when someone from a remote location, connects to the VPN, the IP telephone will be kicked off, and will become unresponsive. If you are on a call on the IP telephone, and you connect to the VPN, from the same home network, the IP telephone connection will be dropped. So first I though it was a firewall rule we had on the router, and I even set the whole router up again, thinking it would fix the problem, but it still acts the same.
So now I don't have any ideas left, and I'm wondering if this even is possible to work together, since both the IP phone and a device connecting trough the VPN, connect to the same public IP, from the same home network.
I hope anyone has any ideas and can help me with this.