In which mode is a port configured to be a member of an EtherChannel without actively participating in LACP negotiations?

When a port is configured to be a member of an EtherChannel without actively engaging in Link Aggregation Control Protocol (LACP) negotiations, it is in the "On" mode. This mode allows the port to automatically bundle without considering the administrative state of the opposite device or negotiating with it through LACP.

In "On" mode, the port will always become part of the EtherChannel as long as there are physically connected interfaces that are also set to "On." This can be beneficial in situations where you have control over both ends of the link and wish to ensure that they will aggregate without negotiation overhead. In contrast, the "Active" and "Passive" modes utilize LACP for negotiations, while "Off" would indicate that an aggregation is not occurring at all. Therefore, the "On" mode is specifically tailored for configurations where the administrator desires a straightforward, no-negotiation approach to EtherChannel creation.