The VPN gateway <b>moon</b> grants access to the subnet behind it to anyone presenting a certificate belonging to a trust chain anchored in the strongSwan Root CA. The hosts <b>carol</b> and <b>dave</b> have certificates from the intermediate Research CA and Sales CA, respectively. Responder <b>moon</b> does not possess copies of the Research and Sales CA certificates and must therefore request them from the initiators <b>carol</b> and <b>dave</b>, respectively.