> # About CFS Regions

> A CFS region is a user-defined subset of switches for a given feature or application in its physical distribution scope.When a SAN is spanned across a vast geography, you may need to localize or restrict the distribution of certain profiles among a set of switches based on their physical proximity. Before MDS SAN-OS Release 3.2.(1) the distribution scope of an application within a SAN was spanned across the entire physical fabric without the ability to confine or limit the distribution to a required set of switches in the fabric. CFS regions enables you to overcome this limitation by allowing you to create CFS regions, that is, multiple islands of distribution within the fabric, for a given CFS feature or application. CFS regions are designed to restrict the distribution of a feature’s configuration to a specific set or grouping of switches in a fabric.

> Note You can only configure a CFS region on physical switches in a SAN. You cannot configure a CFS region in a VSAN.

> Example CFS Scenario: Call Home is an application that triggers alerts to Network Administrators when a situation arises or something abnormal occurs. When the fabric covers many geographies and with multiple Network Administrators who are each responsible for a subset of switches in the fabric, the Call Home application sends alerts to all Network Administrators regardless of their location. For the Call Home application to send message alerts selectively to Network Administrators, the physical scope of the application has to be fine tuned or narrowed down, which is achieved by implementing CFS regions.

> CFS regions are identified by numbers ranging from 0 through 200. Region 0 is reserved as the default region, and contains every switch in the fabric. You can configure regions from 1 through 200. The default region maintains backward compatibility. If there are switches on the same fabric running releases of SAN-OS before Release 3.2(1), only features in Region 0 are supported when those switches are synchronized. Features from other regions are ignored when those switches are synchronized.

> If the feature is moved, that is, assigned to a new region, its scope is restricted to that region; it ignores all other regions for distribution or merging purposes. The assignment of the region to a feature has precedence in distribution over its initial physical scope.

> You can configure a CFS region to distribute configurations for multiple features. However, on a given switch, you can configure only one CFS region at a time to distribute the configuration for a given feature. Once you assign a feature to a CFS region, its configuration cannot be distributed within another CFS region.

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