What Does Expansion Port Mean?
An Expansion port (E_port) is an inter-switch port used in fiber channel topology to connect two fiber switches. An E_port is connected to another E_port to create an inter-switch link (ISL). The E_port carries frames between switches, which are used for fabric management and configuration. It functions as a channel between switches for frames that are intended for Node ports (N_port), Node Loop ports (NL_port) or Nx_ports.
Techopedia Explains Expansion Port
A fiber channel is a high-speed network that connects a number of computer systems and provides a dependable and remote OS interface that requires high bandwidth. The E_port is the point where frames pass between fabric switches. A frame with a destination exits a local switch through an E_port, unless the frame is intended for the switch, N_Port or NL_Port. After a frame passes through the E_port, it is forwarded to a local or final destination.
Each E_port has a unique name within the fabric. An interactive system language (ISL) is used to transmit and receive frames within the fabric, N_port and NL_port. The E_port supports Class 2, Class 3 and Class F services.