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This article describes a limitation in Windows user interfaces where the link speed might not be displayed correctly for high-speed network adapters.
On devices using high-speed network adapters (for example, 400 Gbps or higher), the link speed displayed in Windows user interfaces like Network Connections (ncpa.cpl) might be lower than the actual configured speed.
For example, you might observe a displayed speed of 170.5 Gbps even though the hardware is correctly configured for 600 Gbps.
The link speed exceeds the representable range
This issue is due to a limitation in how certain legacy components query and report link speed information.
Specifically, the Windows user interface retrieves the link speed using a method that returns the result as a 32-bit value, measured in 100-bps units. If the actual link speed exceeds approximately 429.5 Gbps, the value might exceed the representable range and be truncated in the display.
Note
This issue doesn't indicate a malfunction of the hardware or system and doesn't affect the actual performance or functionality of the network adapter.
The system continues to operate at the correct speed as configured at the hardware level.
No action is required unless the display discrepancy causes confusion.
Verify the accurate link speed
To retrieve the accurate link speed, run the following Windows PowerShell cmdlet:
Get-NetAdapter | Select Name, LinkSpeed
This cmdlet returns the accurate speed as reported by modern networking application programming interfaces (APIs), which support higher-capacity adapters.
Status
Microsoft is aware of this limitation and is exploring possible improvements in future updates.