secondary lns forwarding: forward packets to a secondary network server

The Secondary LNS Forwarding feature allows a RAK gateway running in Packet Forwarder mode to send uplink packets to two LoRaWAN® Network Servers simultaneously.

This setup, also called Dual LNS (Multiplexer) mode, designates the Primary LNS to manage device activations, MAC commands, and downlink scheduling. The Secondary LNS functions in uplink-only monitoring mode, receiving packets for observation or redundancy without handling downlinks.

How It Works

1. The gateway receives uplinks from end devices.

2. Packets are forwarded to both the Primary LNS and the Secondary LNS.

   • Primary LNS processes uplinks and sends downlinks.

   • Secondary LNS records uplinks only.

3. Downlink traffic is strictly managed by the primary LNS to prevent conflicts.

Configuring Secondary LNS Forwarding

Secondary LNS Forwarding can only be enabled when the gateway is running in Packet Forwarder mode. Ensure the gateway is operating in this mode before proceeding.

Before connecting the gateway to a LoRaWAN® Network Server, make sure the gateway has been registered on the chosen server.

Configure the Primary LNS

In this example, The Things Network (TTN v3) is configured as the Primary LNS using the UDP protocol.

1. Log in to the gateway’s web UI.

   

2. Navigate to LoRa > Configuration in the left menu.

3. In the Protocol field, select Semtech UDP GWMP from the dropdown list.

   

• If using TTN’s EU1 cluster, confirm the pre-filled server address and port.
• For other regions, update the Server address based on your TTN cluster (port 1700 remains unchanged).

Enable Secondary LNS Forwarding

In this example, ChirpStack v4 is set up as the Secondary LNS, using the LoRa® Gateway MQTT Bridge protocol.

1. On the same LoRa > Configuration page, toggle Secondary LNS Forwarding to enable the feature.
2. Select LoRa® Gateway MQTT Bridge as the protocol.

3. Configure the connection parameters for ChirpStack v4:

   

• MQTT Broker Address: Enter the public IP address of your ChirpStack server, for example: 140.179.175.182 
• MQTT Broker Port: 1883

4. Click Save changes to apply the configuration.

Verification

After setup, uplink packets should appear in both the Primary and Secondary LNS dashboards:

• Primary LNS (TTN v3 via UDP):
  The TTN Console displays live uplink and gateway status messages. TTN also supports sending downlink messages, which are delivered to end devices through the gateway.

  

• Secondary LNS (ChirpStack v4 via MQTT):
  In ChirpStack, the LoRaWAN Frames view shows the uplink frames (e.g., ConfirmedDataUp) received from the same device.

  

This confirms that the gateway is forwarding uplinks to both servers simultaneously, while only the Primary LNS manages downlink traffic.

Troubleshooting

FAQs

1.  Can the Secondary LNS operate without a Primary LNS?
   No. A Primary LNS must always be configured. The Secondary LNS is only for uplink monitoring.

2. What happens if the Primary LNS is unreachable?
   The Secondary LNS will continue receiving uplinks from already-activated devices (ABP). However, OTAA devices cannot join without the Primary LNS.

3. Can the Primary and Secondary LNS use the same protocol?
   Yes, but they must not share the same server address and port. For example, one can use TTN (UDP) and another ChirpStack (UDP), but configured with different endpoints.

Glossary

Updated November 04, 2025 01:39