Cisco Certified Network Associate (CCNA) Practice Exam 2026 – The Comprehensive All-in-One Guide to Exam Success!

The default mode for EtherChannel, when not explicitly defined, is auto. In the context of EtherChannel configurations using the Port Aggregation Protocol (PAgP), "auto" mode allows the switch interface to negotiate and create an EtherChannel if the other end is configured to a mode that allows such negotiation.

When a switch port is set to auto, it listens for PAgP packets and can respond to them if the other end is set to desirable. This makes auto a reactive state where the port will only participate in channel formation under the right conditions, allowing for a plug-and-play type of environment in EtherChannel setups.

This negotiation facilitates the creation of a bundled link that aggregates multiple physical connections into one logical link, enhancing bandwidth and providing redundancy. Other modes such as desirable or on require more active configurations for creating an EtherChannel, indicating that auto is indeed the default behavior to promote ease of implementation without requiring manual intervention.