PAgP Modes

AB

PAgP (Port Aggregation Protocol) is a Cisco proprietary protocol used to automatically group multiple physical ports together to form a single logical link, known as a channel or bundle. PAgP works only on Cisco devices that support it.

There are two modes in PAgP, and a port can be configured to operate in either one of these modes:

1. Desirable: In this mode, a port actively initiates negotiations with the remote end to form a channel. If the remote end also has a port in desirable or auto mode, and PAgP is enabled on both ends, then the negotiation is successful, and a channel is formed.

2. Auto: In this mode, a port does not initiate negotiations with the remote end to form a channel. Instead, it responds to PAgP packets sent by the remote end. If the remote end has a port in desirable mode, and PAgP is enabled on both ends, then the negotiation is successful, and a channel is formed.

Note that the modes of PAgP are compatible with each other, i.e., a port in desirable mode can form a channel with a port in either desirable or auto mode. Similarly, a port in auto mode can form a channel with a port in desirable mode.

The other modes listed in the question (on, active, and passive) are not valid modes in PAgP. The "on" mode is a static mode where the port is manually configured to be a member of a channel without using any negotiation protocol. The "active" and "passive" modes are modes in LACP (Link Aggregation