RBridge ID allocation
RBridge ID assignment is implemented by leveraging proven Domain ID assignment protocols from FC SANs. Request for Domain ID (RDI) and Domain ID Assignment (DIA) protocols ensure that a single switch (the principal switch) centrally allocates the domain IDs for every RBridge in the fabric and detects and resolves any domain ID collisions in the fabric. A Brocade VCS Fabric supports up to 48 RBridge IDs. RBridge IDs can range from 1 through 239.
Only the principal switch can allocate RBridge IDs (domain IDs) for all other switches in the fabric. The principal switch starts the allocation process by allocating an RBridge ID for itself (using the ID value supplied by the user), and initiates the DIA messages on all ports.
Other switches, which are now in subordinate mode, upon receiving the DIA frames respond with an RDI message towards the principal switch. The process continues until all the switches in the fabric have been allocated a unique ID.