Fibre Channel Addressing and Routing Fabric Configuration Process
Stage 2: Principal Switch Selection
Build Fabric Event
Switch joins fabric Sends EFPs on all ISLs
Switches propagate EFPs to all upstream/ downstream switches
EFP EFP EFP
Switches in a multi-switch fabric must coordinate the distribution of Domain IDs to ensure that each switch has a unique Domain ID. One switch in the fabric is responsible for coordinating distribution of Domain IDs. This switch is called the Principal Switch.
The Principal Switch is analogous to the Loop Master, which coordinates the Loop Initialization procedure in an arbitrated loop. Both the Loop Master and the Principal Switch are dynamically selected, and both are responsible for coordinating port address assignment. However, the Loop Master assigns port addresses (AL_PAs), whereas the Principal Switch assigns only Domain IDs. Each switch is responsible for assigning port addresses to each of its attached ports after it receives its Domain ID from the Principal Switch. Within each switch, the function that participates in this process is called the Domain Manager.