<b>iptables -t mangle</b> rules are then used in the PREROUTING chain to mark the traffic to
and from <b>alice</b> and <b>venus</b>, respectively.
<p/>
-The iptables script designated by <b>leftupdown=/etc/mark_updown</b> automatically inserts
-inbound mangle rules that mark the inbound ESP_IN_UDP packets as well as the IPsec-policy rules
+The script designated by <b>leftupdown=/etc/mark_updown</b> automatically inserts
+iptables mangle rules that mark the inbound ESP_IN_UDP packets as well as iptables IPsec-policy rules
that let pass the tunneled traffic. In order to test the tunnel, the NAT-ed hosts <b>alice</b>
and <b>venus</b> ping the client <b>bob</b> behind the gateway <b>sun</b>.
<b>iptables -t mangle</b> rules are then used in the PREROUTING chain to mark the traffic to
and from <b>alice</b> and <b>venus</b>, respectively.
<p/>
-The iptables script designated by <b>leftupdown=/etc/mark_updown</b> automatically inserts
-inbound mangle rules that mark the inbound ESP packets as well as the IPsec-policy rules
+The script designated by <b>leftupdown=/etc/mark_updown</b> automatically inserts
+iptables mangle rules that mark the inbound ESP packets as well as iptables IPsec-policy rules
that let pass the tunneled traffic. In order to test the tunnel, the hosts <b>alice</b>
and <b>venus</b> ping the client <b>bob</b> behind the gateway <b>sun</b>.