> # Information About Fibre Channel Domains

> The Fibre Channel domain (fcdomain) feature performs principal switch selection, domain ID distribution, FC ID allocation, and fabric reconfiguration functions as described in the FC-SW-2 standards. The domains are configured on a per VSAN basis. If you do not configure a domain ID, the local switch uses a random ID.

> This section describes each fcdomain phase:

> - Principal switch selection—This phase guarantees the selection of a unique principal switch across the fabric.
> - Domain ID distribution—This phase guarantees each switch in the fabric obtains a unique domain ID.
> - FC ID allocation—This phase guarantees a unique FC ID assignment to each device attached to the corresponding switch in the fabric.
> - Fabric reconfiguration—This phase guarantees a resynchronization of all switches in the fabric to ensure they simultaneously restart a new principal switch selection phase.

> Caution | Changes to fcdomain parameters should not be performed on a daily basis. These changes should be made by an administrator or individual who is completely familiar with switch operations.

> This section includes the following topics:

> - Domain Restart
> - Domain Manager Fast Restart
> - Switch Priority
> - fcdomain Initiation
> - Incoming RCFs
> - Autoreconfiguring Merged Fabrics
> - Domain IDs
> - Locking the Fabric
> - Committing Changes
> - Clearing a Fabric Lock
> - FC IDs

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