I was reading about this functionality on this wiki (https://en.wikipedia.org/wiki/Port_triggering), and I am unsure what this sentence means in the "disadvantages" section: "On some routers it is possible to have more than one client use port triggering and port forwarding, but not simultaneously." Could someone please make clear why this is?

I understand the general concept of port triggering but not this nuance. Thank you.

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3 Answers 3


A port can only be forwarded to one particular host. A port triggering is nothing more than a triggered port forwarding, when connection is established on port range n to n then port x to x is forwarded to machine The ports are usually forwarded to the same ports on the host.

Port forwarding is used to forward traffic when only one public IP is available. So only connections or communication that was established from a host inside the network can be assigned to the host by the router.

Now, a port forwarding is a static and permanent port forwarding, it gets active when connections or communications are established from the outside which not had been requested / established from the internal network (or all of the time and the router prevents to use those ports for other connections). When a router supports a port forwarding and triggering rule for the same outbound ports then the triggering rule is preferred as it is temporary. There are also routers where you can create an exposed host, so basically all ports are forwarding to this host. But when you add a port forwarding then all ports but not the ports that you just forwarded another host are forwarded to the exposed host.


This isn't that difficult, it just means that only one client at a time can use port triggering and port forwarding, but not 2 or more at the same time.


The way I understand that statement is that you can have multiple clients using port forwarding or port triggering, but you cannot have a single client use port triggering AND port forwarding. Doing so is redundant as the dynamic rule(triggering) created may be identical to the static(forwarding) rule and the resulting behavior may vary from device to device (duplicate traffic, error creating the trigger rule, etc).

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