Introduction
This is a procedure of how to set up a Serial Bridge, aka Serial Tunnel, between two Digi DAL devices.
A serial bridge is a network connection between two serial devices, each of which uses a device server. The serial devices "think" they are communicating with each other across a serial cable using serial communication techniques.
There is no need to reconfigure the server or the serial device. Neither is aware of the intervening network. To configure a serial bridge, you will need two DAL devices with a serial interface.

DAL Serial Bridge (aka Serial Tunnel)
This article will describe how to set up the initiator side (the side in which the traffic starts), and the responder side.
Note: It is possible to set up both sides as the initiator side. If both DAL devices need to initiate traffic, you would set both DAL devices to look like the Initiator Side listed below.
Initiator Side:
- On the menu, click System. Under Configuration, click Serial Configuration.
- Click on the port you are configuring
- For Mode, select Remote Access using the drop down menu.
- Label is Optional
- Click Serial Settings to set the proper Baud rate, Data bits, Parity, Stop bits and Flow control used by the device to which you want to connect.
- Click Autoconnect Settings
- Enable
- Set the Outbound Connection Type to Raw TCP connection, using the drop down.
- Set the Destination to the IP address of the other DAL device. In the example below, the Responder DAL device has an IP address of 10.10.65.80.
- Set the Port to the IP Port for the other side plus 4000 (for Raw TCP). In the example below, the port of the Responder DAL device is 4002 (Port 2 plus 4000 equals 4002).
- Be sure to Apply when complete.

Responder Side:
- On the menu, click System. Under Configuration, click Serial Configuration.
- Click on the port you are configuring
- For Mode, select Remote Access, using the drop down menu
- Label is Optional
- Click Serial Settings to set the proper Baud rate, Data bits, Parity, Stop bits and Flow control used by the device to which you want to connect
- Click Service Settings
- Enable TCP.
- Ensure that the Port is the port of this DAL device plus 4000 (in this example Port 2 plus 4000). It should match the port destination of the Initiator setting above.
- Set the Connection Type to Raw TCP connection, using the drop down.
- Be sure to Apply when complete.

Further Information
If questions or issues on this process, please let us know by creating a Tech Support ticket. To better serve our customers, we have created an online Digi support request form. Please go to complete the form, or use the “CONTACT US” link on our website to access the case form. This will ensure we have all the relevant details and enable us to handle your case as efficiently as possible.
Last updated:
Mar 18, 2025