What is the default mode for PAgP?

The default mode for Port Aggregation Protocol (PAgP) is Auto Mode. In this mode, interfaces are configured to automatically negotiate the establishment of an EtherChannel with another interface that's also PAgP-capable.

When an interface is set to Auto Mode, it will listen for PAgP packets sent by other devices; if it detects a partner that is actively trying to form an EtherChannel, it will respond accordingly. This allows for easier and faster configuration as it reduces the manual effort required to set up link aggregation, fostering seamless integration between switches.

The other modes, such as On Mode, Active Mode, and Passive Mode, serve different purposes and functionality within EtherChannel configurations but are not the default settings. On Mode involves manually configuring the port to form an EtherChannel without negotiation, while Active and Passive Modes are specific to Link Aggregation Control Protocol (LACP) rather than PAgP.