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This section includes the following topics:
FlexAttach virtual pWWN feature facilitates server and configuration management. In a SAN environment, the server installation or replacement, requires interaction and coordination among the SAN and server administrators. For coordination, it is important that the SAN configuration does not change when a new server is installed, or when an existing server is replaced. FlexAttach virtual pWWN minimizes the interaction between the server administrator and the SAN administrator by abstracting the real pWWN using virtual pWWNs.
When FlexAttach virtual pWWN is enabled on an interface, a virtual pWWN is assigned to the server interface. The real pWWN is replaced by a virtual pWWN, which is used for a SAN configuration such as zoning.
Server administrators can benefit from FlexAttach in the following scenarios:
Table 8-1 describes the difference between SAN device virtualization (SDV) and FlexAttach port virtualization.
Table 8-1 Difference Between SDV and FlexAttach Virtualization
The FlexAttach virtual pWWN configuration is distributed for CFS through IPv4, and is enabled by default. The FlexAttach virtual pWWN distribution, by default, is on CFS region 201. The CFS region 201 links only to the NPV-enabled switches. Other CFS features such as syslog is on region 0. Region 0 will be linked through IPv4 for all NPV switches on the same physical fabric. If CFS has an option to link through IPv4 or ISL, then CFS will select the ISL path.
Note NPV switches do not have ISL (E or TE ports) and are linked through IPv4.
Security settings for the FlexAttach virtual pWWN feature are done by port security at the NPV core. Node WWN of the end device is used to provide physical security.
For more details on enabling port security, refer to the Cisco MDS 9000 Family NX-OS Security Configuration Guide.
Following are recommended guidelines and requirements when deploying FlexAttach virtual pWWN:
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Automatic assignment of virtual pWWN can be configured on an NPV switch globally, per VSAN, or per port. When assigned automatically, a virtual WWN is generated from the device local switch WWN.
The port must be in a shut state when the virtual pWWN is enabled.
To assign a virtual pWWN automatically, perform this task:
You can manually assign a WWN to the interface, without generating it through the switch. Several checks are done by the NPV core to ensure the uniqueness of virtual pWWNs in the switch. When duplicate virtual pWWNs are configured, the subsequent logins are rejected by the NPV core switch.
To assign virtual pWWN manually, perform this task:
You can configure virtual pWWNs through real pWWNs. This process is required for NPIV hosts containing multiple pWWNs, of which only FLOGI is mapped to the virtual pWWN. Subsequent FDSIDs will have different mappings.
Several checks are done by the NPV core to ensure the uniqueness of virtual pWWNs in the switch across the NPV switches. When duplicate virtual pWWNs are configured, the subsequent logins are rejected by the NPV core switch.
To map pWWN to virtual pWWN, perform this task:
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To display FlexAttach configuration information, perform one of the following tasks:
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Displays if the end device is logged with the correct virtual WWNs. |
For detailed information about the fields in the output from these commands, refer to the Cisco MDS NX-OS Command Reference.
To view and confirm that the type and value of virtual pWWNs are correct, enter the show flex-attach virtual-wwn command. (See Example 8-1.)
Example 8-1 Displaying the Type and Value of Virtual pWWNs
To verify that the end device is logged with the correct virtual WWNs, use the show fcns database command on the NPV core. (See Example 8-2.)
Example 8-2 Verifying the End Device
Table 8-2 lists the errors that might be displayed and provides the workarounds.
Table 8-2 FlexAttach Errors and Workarounds