How does Port Trigger works?

[Arawn]

Hi!

First, I know what Port Trigger is about. What I want to know are the conditions that maintain open the dependent ports.

Let me explain my question. I know that traffic at the trigger port opens the specified incoming ports, but still not sure the specific sequence of events. The manual that came with the router shows an old firmware (Port Mapping), and the explanation at the web console is ambiguous.

The trigger port acts on incoming or outgoing traffic? If the open ports are for external traffic, I deduce the trigger port is for internal request, otherwise the router cannot know where to route the incoming traffic...

Do the open ports stay open indefinitely, or are timed out, or close on lack of traffic, time dependent? Is this kind of behaviour, if true, dependent on the trigger port or open ports?

Hope you can see that I wish to understand completely the workings of Port Trigger.

Hope someone can explain this to me.

My thanks in advance.

[Oleg]

Broadcom calls this feature autofw (autoforwarding). Theoretically it does work as follows. Suppose, the external server answers to your queries at port 4444, In request to it this server should connect to your PC to port like 5555. In such a setup you should set 4444 as trigger port, in this case wl500g will forward all requests to port 5555 to your PC. Yes, it does have a timeout.
I've not checked the details yet, but full source code is provided.

[Arawn]

Thanks, Oleg.

I'll take a look at the source code... though I'm not familiar with network code, I think I can manage.

But you gave me the information I needed to get the basic ideia, thx.

Best regards.

[Rob ter Veer]

Hmmm.. I don't get it. I'm trying to enable WINMX autoportforwarding. Set up the router as folows:

undefined
Trigger Port Protocol Incoming Port Protocol
6699 TCP 6699 TCP
6257 UDP 6257 UDP


But ports don't seem to be forwarded to my winmx client. How can I check forwarding is triggered and how can I determine which outgoing ports are being used? I assume the outgoing port is the trigger port?

[Tamadite]

You have a host on your LAN that is to start a communication with a host on the WAN port. When the host on the LAN sends its packet to the WAN host, there you have "trigger port".

The host on the WAN port will send you a packet based on the LAN host request. There you have the "incoming port".

How the router knows where to send the incoming traffic? The router will send the incoming traffic to the LAN host that triggered the "trigger port".