Which method uses a proprietary protocol in EtherChannel configuration?

The correct choice is Port Aggregation Protocol (PAgP), which is a Cisco proprietary protocol used for EtherChannel configurations. PAgP allows switches to automatically negotiate and form EtherChannel links by exchanging packets. This protocol ensures that the settings on both ends of the link are compatible and can automatically manage the aggregation of multiple physical links into a single logical channel.

PAgP operates in two modes: the desirable mode, where a switch actively seeks to join an EtherChannel, and the auto mode, where a switch will form an EtherChannel if a neighboring switch tries to negotiate one. The use of a proprietary protocol means that PAgP works specifically within Cisco environments, but it is not supported by non-Cisco devices.

In contrast, Link Aggregation Control Protocol (LACP) is an industry-standard protocol found in multiple vendor devices, making it interoperable outside the Cisco environment. Static Link Aggregation does not use any negotiation protocol, instead requiring manual configuration. Dynamic Link Aggregation could refer to either LACP or protocols like PAgP, but since the question specifies a proprietary method, PAgP is the clear answer.