Port Triggering – What is it?

Port Triggering is a new feature supported by the Vigor router that allows a host machine to dynamically and automatically forward a specific port back to itself. Trigger Port is the outgoing (destination) port that the application uses.

What is Port Triggering?

Port Triggering is similar to port forwarding a device, but there are a few differences. If you are a network or system admin, it might be important to know how to port triggering works. It is best suited for port forwarding multiple devices simultaneously, and it is highly secure too. Here is a detailed breakdown to understand it better. This process handles communication between external and internal IP networks or host machines via a NAT-enabled router. NAT means Network Address Translation, which filters multiple IP addresses and turns them into a single IP address on a local area network. Your NAT router will be responsible for checking internet traffic within the local area network (LAN).

So, when you open a port for another network or server, port triggering will open it upon your request and close it when you are not using it. The port expires automatically, which makes it safer for you because no one can intercept the traffic. In short, it is an outgoing connection that creates, or more precisely triggers, an incoming port forwarding that expires when the traffic is left idle.

port triggering

Uses Of Port Triggering

Enlisted below are the uses:

  • It is used when the users want to use the port forwarding to reach out to various hosts located at the remote end.
  • It is also used when the running application requires the incoming port to differ from the outgoing port.
  • It is needed when the user wants to connect and stay online for a long duration for an application like gaming and video conferencing. This provides the stability in connection.
  • It is needed to establish a secure VPN network between the home and office network.

How does it work?

When port triggering, you need a router to monitor traffic within the network and you will specify a trigger port that will send outbound data. The router will then log the IP address of the computers which sends traffic to the trigger port. It will also open incoming ports then forward traffic to that location. For instance, if you are port triggering, you can set a rule stating “when data flows from port 25, it will forward it to port 40.” When your router sees data flowing from port 25, it will execute the triggering rule by forwarding 25 to 40 and effect port triggering. Upon sending this data, it will close all the ports until it detects traffic on port 25. Upon detection, it will open the specific ports and continue the cycle. Therefore, a successful port triggering is dependent on the user choosing a triggering port and specifying the incoming ports they want to use. This makes it a safe configuration as ports that are not in use will close, minimizing hacker attempts.

Also to note in port triggering is the concept of a timer. The timer will track the duration which the ports are open, after which it closes automatically. This means that you will need a new connection if you receive new data after the timer resets. Given this limitation, a server looking for information from your computer will not connect until the port is open.

How do I set up?

Step 1: Log in to your router’s setup page from your internet browser.

Step 2: Go to the Port Forwarding Trigger or Port Forwarding page.

Step 3: Enter a port number and choose Add Service.

Step 4: Mention the details of outbound packets to trigger ports. To do that, you have to pick a unique name and choose Any from the drop-down list. Now, select the IP addresses of devices you wish to port trigger and the service type.

Step 5: Enter the details of inbound packets that you wish to port forward by selecting the connection type. Also, you have to fill the starting and ending port fields.

Step 6: Once you are done with that, click Apply.

port triggering

When is it used?

Typically, it is used when the user needs to use port forwarding to reach multiple computers on the same IP address. At the same time, it is also used when applications need to open incoming ports that are different from the outgoing port.

Network administrators also use it to find or configure a port to one local computer. It is considered to be dynamic because ports are opened when they are needed and closed when they aren’t in use.

Is it risky?

While port triggering is safer than port forwarding, it is not entirely secure given the limited time the ports are left open. When your ports are open, a hacker can learn your IP address and port details. With these details, they might still access your network, just like in port forwarding.


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