The situation is this: there is a physical server with installed Asterisk. To this server via USB connected to a GSM modem (Huawei E173), which uses Asterisk via the module chan-dongle. This configuration is fully debugged and working.
There was a need to connect to Asterisk as a gateway 1-n the same modem. The problem is that this modem should be located in a different region.
To start, prepare the modem took a router with OpenWrt and a USB port, configured the VPN tunnel with the Asterisk server.
Question: how most competently and reliably to implement the idea:
1. Set on router 1-n Asterisk module chan-dongle, which is then used by the primary server as a SIP trunk;
2. To traverse the USB device over the network to the server using, for example, USB over IP tunnel;
3. The other?
I would be very grateful to hear Your opinions and suggestions for implementation.