Chris Green  wrote:
> OK, my current WiFi set up is (as a mobile connection would be) behind
> a NAT router and I set up reverse ssh tunnels to allow me to connect
> 'on demand' to the Pi (BBB).  So I can do exactly the same using the
> mobile data connection.
>
> Will the mobile provider object to the connection being up all the
> time but with virtually no data going through it?

Mobile networks are often quite aggressive at killing idle connections
through their CG-NAT - 30 seconds idle is common, for example.  To avoid
that you have to send keepalives, which will gradually consume your data
allowance.

Sending packets from your device is fine - you can just set up a new
connection.  But receiving is difficult if the NAT mapping has gone away, so
the external machine can't reach you.  I'm not sure if there's a VPN
protocol that handles this appropriately without using keepalives.

It may be that using IPv6 avoids this problem.

Theo

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