Resolve Link Addresses

Overview

The dnp3linkaddr tool is designed to discover the link address of a DNP3 outstation. Since many DNP3 deployments require knowledge of the correct remote link address before initiating communication, this tool provides automated resolution methods instead of relying on brute force.

The tool currently uses two approaches:

1. Self-Address Method Send a REQUEST_LINK_STATUS message using the Self address (0xFFFE). If the outstation supports this optional feature, it will reply with its configured link address.

2. Passive Listening Method Listen for REQUEST_LINK_STATUS messages periodically sent by the outstation (as required by DNP3 specification section 9.2.6.5). This allows link address resolution without requiring the Self address feature.

Note

Some outstations poll at different intervals — typically between 5 and 60 seconds. You may need to wait for up to a full cycle before receiving a REQUEST_LINK_STATUS frame. Be patient, especially when relying solely on the passive listening method.

Usage

Resolve using the Self-Address method (default):

dnp3linkaddr 127.0.0.1

This will attempt to send a REQUEST_LINK_STATUS message using the Self address. If the outstation supports it, the tool will display the resolved link address.

Resolve by waiting for a periodic status request:

dnp3linkaddr 127.0.0.1 -no-self -interval 45

This disables the Self method and waits up to 45 seconds for the outstation to send a REQUEST_LINK_STATUS message.

Practical Notes

• The Self-Address method is not mandatory in DNP3 and may not be implemented by all outstations.

• The passive listening method is more reliable but depends on the polling cycle of the outstation.

• Always verify that the local link address (--listen) matches what the outstation expects from the master.

Hint

• Ain’t nobody got no time for that - but patience is key here: some devices only send REQUEST_LINK_STATUS messages once every 60 seconds.