Comparison of Access Gateway, ISL, and FC switch ports
A switch in Access Gateway (AG) mode uses VF_Ports and N_Ports to connect devices to the Fibre Channel (FC) switch. The connected FC switch connects to the AG switch N_Ports through F_Ports and presents a variety of ports for connection to FC fabric devices.
Access Gateway (AG) multiplexes host connections to the fabric. AG presents a VF_Port to a FCoE host and an N_Port to an edge Fibre Channel fabric switch. Multiple VF_Ports mapped to N_Ports provide multiple device ports for connection to the FC fabric.
Using N_Port ID Virtualization (NPIV), AG allows multiple FCoE initiators to access the SAN on the same physical port. This reduces the hardware requirements and management overhead of hosts to the SAN connections.
In contrast to the AG switch, the connected FC switch presents F_Ports (or FL_Ports) to storage devices hosts and presents E_Ports, VE_Ports, or EX_Ports to other switches in the fabric.
A native switch using an ISL connection between its FC E_Port and an EX_Port on an FCR consumes domain ID resources that may impact scalability as VCS and FC fabrics grow. In addition, connection through a FCR may limit connection to multivendor FC fabrics. Finally, connection through an ISL provides limited device port connections to the FC fabric. For more information on configuring FC ports for connection to an FCR and FC fabric, refer to Configuring Fibre Channel Ports.