| A tunnel that will connect the subnets behind the gateways <b>moon</b> |
| and <b>sun</b>, respectively, is preconfigured by installing a %trap eroute |
| on gateway <b>moon</b> by means of the setting <b>auto=route</b> in ipsec.conf. |
| A subsequent ping issued by client <b>alice</b> behind gateway <b>moon</b> to |
| <b>bob</b> located behind gateway <b>sun</b> triggers the %trap eroute and |
| leads to the automatic establishment of the subnet-to-subnet tunnel. |
| <p> |
| <b>leftfirewall=yes</b> automatically inserts iptables-based firewall rules |
| that let pass the tunneled traffic. |
