I am having an issue with my smartphone device and packets monitoring: I am trying to find a reason why I cannot establish a VPN connection via PPTP protocol.
I have the following successful scenario:
- Device set using IPv4
- Connecting to VPN OK
Now a failing scenario:
- Device set using IPv6
- Connecting to VPN fails (after 30s timeout)
tcpdump result and found out the following: during exchanges for connection establishment, both IPv6 and IPv4 scenario are the same until my device is sending a "PPP LCP Configuration-Request" to server.
Then a Ack comes back from server for IPv4 scenario, and nothing comes back for IPv6 scenario. On server side they affirm that in both scenario the Ack is send back.
tcpdumpdoes not show this packet, does that mean it has not been received ?
- If this packet have been received but "dropped", how can I find out (tools, methodology) ?
I am not a Linux nor a network expert so I might miss some trivial hints.
Linux version 3.10.40