Cisco Certified Network Associate (CCNA) Practice Exam

In the context of Link Aggregation Control Protocol (LACP), a port operating in active mode actively participates in LACP negotiation, which is essential for establishing a logical link aggregation group (LAG) between two or more devices.

When a port is set to active mode, it transmits LACP packets to other devices to negotiate the formation of an aggregated link. This proactive approach means that the active port is always trying to communicate with its peer ports to ensure that link aggregation is properly configured and maintained. The active mode also allows the port to respond to LACP packets from other ports, facilitating a smooth negotiation process.

In contrast, a port set to passive mode will not initiate LACP negotiations; it will only respond to LACP packets that it receives. This means that while a passive port can be part of an aggregated link, it does not take the initiative to create that link, as an active port would. Other modes, such as "On" and "Desirable," pertain to different contexts of link aggregation but are not framed in the context of LACP negotiation.

Therefore, the active mode is the only one that ensures both negotiation initiation and response, making it the correct answer for the mechanism of LACP negotiation.