> # Guidelines and Limitations

> As of MDS NX-OS Release 4.1(1a), the following conditions must be considered when configuring the virtual device failover attributes:

> - The attribute configuration is supported only with MDS NX-OS Release 4.1(1a) and later. In a mixed mode fabric where earlier releases are combined, the attribute configuration will fail.
> - When the failover attribute is configured, if the primary device is offline then the secondary device becomes active.
> - When the failover attribute is deleted after the primary device failover to the secondary device, then the primary becomes active if the primary device is online. If the primary device is not online, then the SDV virtual device is shut down.

> Note The SDV attributes configuration is supported in Cisco DCNM for SAN Release 4.1(2) and later.

> This section includes the guidelines and limitations for this feature:

> - SDV Requirements and Guidelines
> - Guidelines for Downgrading SDV
> - Downgrading with Attributes Configured
> - Downgrading with Virtual Initiators Configured
> - Downgrading with SDV LUN Zoning Configured

> Copyright 2010-2013, Cisco Systems, Inc. All rights reserved.