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Port triggering

Port triggering definition

Port triggering is a networking technique used to dynamically open specific ports on a router or firewall when certain outbound traffic is detected. It is an alternative to port forwarding, which requires manual configuration of specific port mappings.

Port triggering is often used when multiple devices on a local network need to communicate with servers or services using the same ports. Instead of mapping ports to individual devices (as done in port forwarding), port triggering opens and closes ports based on the specific triggering events. Port triggering does not provide the same level of control and security as port forwarding, as the incoming ports are opened temporarily and for a specific triggering event.

See also: network port

How port triggering works

  1. 1.Outbound connection. When a device on the local network initiates an outbound connection to a specific destination IP address and port, the router or firewall monitors this connection.
  2. 2.Triggering event. The triggering event occurs when the outbound connection matches predefined criteria. These criteria are typically based on the source IP address, destination IP address, and/or destination port.
  3. 3.Port opening. When the triggering event is detected, the router or firewall dynamically opens the specified incoming port or ports associated with the triggering event. This allows the incoming traffic to reach the device on the local network that initiated the outbound connection.
  4. 4.Timeout. After a period of inactivity or when the connection is closed, the router or firewall will eventually close the opened port as per the configured timeout period.