Device aliases have the following features:

• The device alias information is independent of the VSAN configuration.

• The device alias configuration and distribution is independent of the zone server and the zone server database.

• The device alias application uses the Cisco Fabric Services (CFS) infrastructure to enable efficient database management and distribution. Device aliases use the coordinated distribution mode and the fabric-wide distribution scope.

• Basic and enhanced modes.

• Device aliases used to configure zones are displayed automatically with their respective pWWNs in the show command output.

Device aliases have the following requirements:

• You can only assign device aliases to pWWNs.

• There must be a one-to-one relationship between the pWWN and the device alias that maps to it.

• A device alias name is restricted to 64 alphanumeric characters and may include one or more of the following characters:

  • a to z and A to Z

  • Device alias names must begin with an alphabetic character (a to z or A to Z).

  • 1 to 9

  • - (hyphen) and _ (underscore)

  • $ (dollar sign) and ^ (up caret)

When operating in basic mode, which is the default mode, the device alias is immediately expanded to a pWWN. In basic mode, when device aliases are changed to point to a new HBA, for example, that change is not reflected in the zone server. Users must remove the previous HBA's pWWN, add the new HBA's pWWN and then reactivate the zoneset.

Note	Cisco NX-OS Release 9.3(3) supports only the basic mode. Beginning Cisco NX-OS Release 9.3(5), both basic and enhanced device alias modes are supported.

When operating in enhanced mode, applications accept a device alias name in its native format. Instead of expanding the device alias to a pWWN, the device alias name is stored in the configuration and distributed in its native device alias format. So application such as zone server can automatically keep track of the device alias membership changes and enforce them accordingly. The primary benefit of operating in enhanced mode is that you have a single point of change.

Whenever you change device alias modes, the change is distributed to other switches in the network only if device alias distribution is enabled or on. Otherwise, the mode change only takes place on the local switch.

Note	Enhanced mode, or native device alias-based configurations, are not accepted in interop mode VSANs. IVR zoneset activation fails in interop mode VSANs if the corresponding zones have native device alias-based members.

Device Alias services have these configuration guidelines and limitations:

• If two fabrics running in different device alias modes are joined together, the device alias merge fails. There is no automatic conversion to one mode or the other during the merge process. In this situation, you must select one mode over the other.

• Before changing from enhanced to basic mode, you must first explicitly remove all native device alias-based configurations from both local and remote switches, or replace all device alias-based configuration members with the corresponding pWWN.

• If you remove a device alias from the device alias database, all applications automatically stop enforcing the corresponding device alias. If that corresponding device alias is part of an active zone set, all the traffic to and from that pWWN is disrupted.

• Renaming the device alias not only changes the device alias name in the device alias database, but also replaces the corresponding device alias configuration in all of the applications.

• When a new device alias is added to the device alias database, and the application configuration is present on that device alias, it automatically takes effect. For example, if the corresponding device alias is part of the active zoneset and the device is online, then zoning is enforced automatically. You do not have to reactivate the zone set.

• If a device alias name is mapped to a new HBA’s pWWN, the application’s enforcement changes accordingly. In this case, the zone server automatically enforces zoning based on the new HBA’s pWWN.

By default, device alias distribution is enabled. The device alias feature uses CFS to distribute the modifications to all switches in a fabric.

If device alias distribution is disabled, database changes are not distributed to the switches in the fabric. The same changes would have to be performed manually on all switches in the fabric to keep the device alias database up-to-date. Database changes immediately take effect, so there would also not be any pending database and commit or abort operations. If you have not committed the changes and you disable distribution, a commit task fails.

Note

CFS is enabled by default. All devices in the fabric must have CFS enabled, or they do not receive distributions.If CFS is disabled for an application, that application does not distribute any configuration, and it does not accept a distribution from other devices in the fabric. To enable CFS use the cfs distribute command.

This example shows how to display a failed device alias status:

switch# show device-alias status

Fabric Distribution: Disabled

Database:- Device Aliases 25

Status of the last CFS operation issued from this switch:

==========================================================

Operation: Commit

Status: Failed (Reason: Operation is not permitted as the fabric distribution is

 currently disabled.)

When you perform any device alias configuration task (regardless of which device alias task), the fabric is automatically locked for the device alias feature. Once you lock the fabric, the following situations apply:

• No other user can make any configuration changes to this feature.

• A copy of the effective database is obtained and used as the pending database. Subsequent modifications are made to the pending database. The pending database remains in use until you commit the modifications to the pending database or discard (abort) the changes to the pending database.

You can use locking operations (clear, commit, abort) only when device alias distribution is enabled. If you have performed a device alias task and have forgotten to release the lock by either committing or discarding the changes, an administrator can release the lock from any switch in the fabric. If the administrator performs this task, your changes to the pending database are discarded and the fabric lock is released.

The changes are only available in the volatile directory and may be discarded if the switch is restarted.

To use administrative privileges and release a locked device alias session, use the clear device-alias session command in EXEC mode.

switch# clear device-alias session

This example shows how to display the status of the clear operation:

switch# show device-alias status

Fabric Distribution: Enabled

Database:- Device Aliases 24

Status of the last CFS operation issued from this switch:

==========================================================

Operation: Clear Session<--------------------Lock released by administrator

Status: Success<-----------------------------Successful status of the operation