As a test setup I have an Asterisk server that two SIP clients can access via an OpenVPN connection. Both devices use OpenVPN Connect and get assigned an address from the pool 10.61.1.0/24. The Asterisk server runs at 10.61.1.1.
When the SIP clients are in my home network they will not receive calls.
I’ve narrowed it down as follows:
- Functionality is normal in any other network (for example my mobile hotspot).
- Calling extensions works, only receiving calls does not.
- Network communications are normal, as traffic flows properly (Client 1 => Asterisk server => Client 2)
- Wireshark on the “called” device shows incoming SIP traffic from the asterisk server, but it only shows up as “Fragmented IP protocol”, never any complete packets.
Here is a Wireshark screenshot of a “broken” incoming call that doesn’t ring:
In comparison, here is a Wireshark screenshot of the exact same event when in any different network:
The only difference between the two situations is the Wifi network that the clients are in.
I’d be very thankful if anyone had any ideas on what could be causing this.