What happens when auto-negotiation is enabled and devices negotiate speed and duplex?

• A. Devices automatically negotiate the best common speed and duplex.
• B. They must be manually configured.
• C. They reset to a default 100 Mbps half-duplex.
• D. They disable flow control.

Answer: (A)

Auto-negotiation lets two Ethernet devices advertise their capabilities and agree on the best common configuration. When enabled, each side shares what speeds and duplex modes it supports, and they settle on the highest speed and full-duplex option that both can use. This provides optimal performance without manual tuning. It’s not about resetting to a fixed default, and flow control isn’t automatically disabled by negotiation—flow control is a separate capability that may be negotiated or configured independently. So, the best description is that devices automatically negotiate the best common speed and duplex.