SunSpec Model 11 — Ethernet Link Layer
SunSpec Model 11 is a standardised Ethernet Link Layer information model defined by the SunSpec Alliance, present in the Modbus TCP register chain of SunSpec-compliant devices such as inverters, gateways, and energy management controllers. The template reads the interface identifier, model length, current link speed, configuration status bitfield, and operational state, and exposes two read-write registers: a user-defined interface name and a forced link speed setpoint. Having this data in the ModbusCloud portal lets you verify network health alongside energy data without a separate network tool.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 8, read and write
- Brand
- SunSpec
- Last updated
Registers (8)
8 read, 3 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| id | Read | ||||
| l | Read | ||||
| spd | Mbps | Read | |||
| cfgst | Read | ||||
| st | Read | ||||
| nam | Read and write | ||||
| ctl | Read and write | ||||
| frcspd | Mbps | Read and write |
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If a device is not in the library yet, we build the template for free as soon as we have the register data.
Use cases
- Monitor the Ethernet link speed register to confirm the device negotiated the expected 100 Mbps connection after installation.
- Alert on changes to the operational state register to detect unexpected interface shutdowns during overnight low-load periods.
- Track the configuration status bitfield over time to spot intermittent autonegotiation failures or hardware fault flag assertions.
- Verify that the forced speed setpoint matches your site network policy after firmware updates reset the register to defaults.
- Compare interface name values across multiple SunSpec gateways in the portal to confirm each device is correctly labelled in your asset register.
Installation
Enable Modbus TCP on the SunSpec-compliant device by navigating to the communication or Modbus section of its web interface and setting the TCP port, typically 502.
Connect the device to the same LAN segment as the ModbusCloud Gateway, ensuring no firewall blocks TCP port 502 between the two.
In the ModbusCloud portal, add the device as a new data source, import this SunSpec Model 11 template, and assign the correct Modbus unit ID as configured on the device.
Spot-check the template by reading the id register: a value of 11 confirms the model block is reachable and the address offset is correct.
Things to watch for
Why do I get a Modbus exception reading Model 11 registers?
Some SunSpec devices raise a Modbus exception if you request a strict subset of registers within a multi-register field such as the MAC address block. Read the entire Model 11 block in a single request rather than polling individual registers. If the device follows SMA conventions, the block may return all NaN values by design, which is normal.
The spd register returns 0 or NaN. What does that mean?
A zero or NaN on the spd register usually means the Ethernet link is not established, or the device implements Model 11 for compatibility only and populates registers with NaN placeholders. Verify the physical cable and switch port, then check the st register: a value other than ENABLED (1) confirms the interface is not active.
No values appear after importing the template. The gateway is connected.
Confirm the base address offset used by the device. SunSpec profiles on many devices start at register 40001, so the Model 11 block sits at an offset from that base. Check that the unit ID in the portal matches the one configured on the device, typically 1 for direct TCP connections or 125 to 126 for SMA gateway units.
Is it safe to write to the ctl or frcspd registers on a live device?
Use caution when writing to the ctl and frcspd registers. Forcing a speed setting incompatible with the connected switch will drop the Ethernet link and disconnect the device from the cloud portal entirely, requiring physical access to recover. Always verify the target speed against the switch port capability before writing, and schedule writes during a maintenance window.
Knowledge base articles for this device
SunSpec Modbus: one register map for many inverters
SunSpec Modbus is the open register map SMA, Fronius, SolarEdge and Kostal share. The layout, int+SF vs float, the TCP port per brand and reading a mixed fleet.
Fronius Modbus: read a Symo GEN24 over Modbus TCP
Fronius Modbus explained: enable Modbus TCP on the Symo GEN24 on port 502, choose between int+SF and float, read the right SunSpec registers and scale them correctly. Practical guide for solar installers.
SMA Modbus: reading a Sunny Boy over Modbus TCP (installers)
SMA Modbus explained: enable the Modbus TCP server on port 502, choose between the SMA profile (unit ID 3) and SunSpec (unit ID 126), read the right registers, and handle the NaN values at night. Practical guide for installers.
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