A tunnel connecting the subnets behind the gateways <b>moon</b> and <b>sun</b>,
respectively, is automatically established by means of the setting
<b>start_action = start </b> in swanctl.conf.
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The connection is tested by client <b>alice</b> behind gateway <b>moon</b> pinging
the client <b>bob</b> located behind gateway <b>sun</b>. The updown script
automatically inserts iptables-based firewall rules that let pass the tunneled traffic.
