Select the three PAgP channel establishment modes. (Choose three.)

PAgP (Port Aggregation Protocol) is a Cisco-proprietary protocol used to automatically aggregate multiple physical ports into a single logical link. There are three modes that can be configured on a Cisco switch port for the establishment of a PAgP EtherChannel:

1. Desirable: In this mode, the interface actively attempts to negotiate a PAgP EtherChannel. It initiates negotiations with other ports by sending PAgP packets.
2. Auto: This mode places an interface in a passive negotiating state. In this state, the interface responds to PAgP packets it receives but does not initiate PAgP negotiation.
3. On: This mode forces the channel to be up without any PAgP negotiation. In essence, this is a manual configuration, and both ends of the EtherChannel must be set to ‘on’ for the link to be part of the EtherChannel.

The other modes mentioned are related to LACP (Link Aggregation Control Protocol), which is another protocol used for port channeling, not PAgP:

• Active and Passive are LACP modes, where ‘active’ means the port actively tries to form an LACP EtherChannel, and ‘passive’ waits for another port to request to form an LACP EtherChannel.
• Blocking is not a mode for EtherChannel; it is a state used in Spanning Tree Protocol to prevent loops by blocking redundant paths.

So the correct PAgP channel establishment modes are Desirable, Auto, and On.