A type of port forwarding where outbound traffic on predetermined ports sends inbound traffic
to specific incoming ports. Port triggering “triggers” an open incoming port when a client on the local network makes an outgoing connection to a predetermined port
on a server. Port Triggering is more secure than port forwarding, because the incoming ports are not open all the time, they are open only when a program is actively using the trigger port. One major advantage of port triggering is that it allows computers behind a NAT
to provide services which would normally require a static
host (one with an unchanging network address). The disadvantage of port forwarding is that it only allows one client on the network to use a particular service that occupies a particular port.