[strongSwan] No packets transmitted for a while over IPv6 after connection establishment

[Jason White]

Having looked at the archives of earlier discussions (including mine from a
few years ago), there were path MTU discovery issues involved when I last
tried to set this up.

An IPv6 connection between two StrongSwan instances running on the local
network is fine, so it's related to the PPP connection to the outside. The MTU
of the PPP link is 1496 bytes, as the ISP drops larger packets.

I'll keep investigating, but if someone could remind me what has to be done to
configure StrongSwan so that path MTU discovery works, I can adjust my
configuration accordingly.

Once this is sorted out it would be a good example for the wiki.