What is autonegotiation designed to do on a link?

• A. Manually setting fixed speed and duplex.
• B. Synchronizing devices to a single time source.
• C. Negotiating the best speed and duplex settings automatically.
• D. Blocking unauthorized MAC addresses.

Answer: (C)

Autonegotiation on a network link is about two connected devices exchanging their capabilities and agreeing on the highest speed and duplex mode they both support. This lets the link operate at the fastest common settings without manual configuration and helps avoid duplex mismatches that can slow things down or cause collisions. Essentially, both sides advertise what they can do (speed options like 10/100/1000 Mbps and duplex modes) and agree on the best compatible pair to use. Some devices may also negotiate optional features like flow control, but the core purpose is to set the optimal speed and duplex automatically.

The other choices describe things that aren’t about link capability negotiation: manually fixing speed and duplex disables autonegotiation, synchronizing time sources relates to clock protocols, and blocking unauthorized MAC addresses is a security control, not a mechanism for negotiating link settings.