A connection between the hosts <b>moon</b> and <b>sun</b> is set up.
The authentication is based on <b>X.509 certificates</b> and the <b>kernel-libipsec</b>
plugin is used for userland IPsec ESP encryption. <b>Firewall marks</b> are used to make
the direct ESP connection possible and still allow IKE traffic to flow freely between
the two hosts.
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Upon the successful establishment of the IPsec tunnel, an updown script automatically
inserts iptables-based firewall rules that let pass the traffic tunneled via the
<b>ipsec0</b> tun interface. In order to test both host-to-host tunnel and firewall,
<b>moon</b> pings <b>sun</b>.