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How to resolve a duplex mismatch error

If your network is down and a log indicates a duplex mismatch error, this may be caused by a failure in the auto-negotiation setting for duplex and speed in different Ethernet ports, or it may be caused by a mismatch between the hard-coded settings.

To diagnose and resolve the problem, check the existing settings and hard-code both devices with the identical settings. Even if this resolves the issue, you may want to go further to get to the root cause of the issue. Test with different settings (e.g., half duplex vs. full duplex) at different times to see if there’s a problem that occurs at one of those settings. That can help you see if there may be an underlying issue beyond the auto-negotiation step.


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