Auto-negotiation lets two devices agree on speed and duplex settings. When you plug in a cable, both ends advertise their capabilities. They pick the highest speed both support. If auto-negotiation fails on one end, you get duplex mismatch. This causes slow speeds and packet loss. Always enable auto-negotiation on both ends, or manually set identical values on both.
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$ curl repovive.com/roadmaps/network-design/physical-and-data-link-fundamentals/auto-negotiation
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