A connection between the subnets behind the gateways moon and sun is set up. The authentication is based on X.509 certificates containing RFC 3779 IP address block constraints. Both moon and sun set rightsubnet=0.0.0.0/0 thus allowing the peers to narrow down the address range to their actual subnets 10.1.0.0/16 and 10.2.0.0/16, respectively. These unilaterally proposed traffic selectors must be validated by corresponding IP address block constraints.

Upon the successful establishment of the IPsec tunnel, leftfirewall=yes automatically inserts iptables-based firewall rules that let pass the tunneled traffic. In order to test both tunnel and firewall, client alice behind gateway moon pings client bob located behind gateway sun.