Difference between FCAlias & Device-Alias

FC aliases are used to associate 1 or more PWWNs to a user friendly name.  FCaliases are VSAN specific, so if a device is moved from VSAN 1 to VSAN 2, you should delete the FCalias in VSAN 1 and create a new one in VSAN 2.  FCalias will interoperate with some non-Cisco fibre channel switches.FCaliases are propagated via a zoneset  activate.

Device aliases associate 1 PWWN to a user friendly name.  They are not vsan sepcific, and can be used for other features beside zoning.  Device Aliases are configured manually in each switch, or can be propagated via Cisco Fabric Services.There is a Device Alias mode known as enhanced  mode, which is not enabled unless configured.  With enhanced mode device alias, if an HBA is associated with a device alias, and that device alias is placed into 20 zones, then that HBA fails and is replaced so the PWWN changes, you can edit the device alias database and that will push the new PWWN into the 20 zones automatically.


replace XXX with the appropriate VSAN number):

switch(config)# fcalias name stor-array-processor-a vsan XXX
switch(config-fcalias)# member pwwn AA:BB:CC:DD:EE:FF:00:11
switch(config-fclias)# exit
switch(config)#


To create a device alias, you’ll use the device-alias database command in global configuration mode. Once you are in database configuration mode, you can create device aliases using the device-alias command, like this:


mds(config)# device-alias database
mds(config-device-alias-db)# device-alias name <Friendly name> pwwn <Fibre Channel WWPN>
mds(config-device-alias-db)# exit
mds(config)# end

There is an additional step required after defining the device aliases. You must also commit the changes to the device alias database, like this:

mds(config)# device-alias commit


This commits the changes to the device alias database and makes the device aliases active in the switch.

Once a device alias is created, it applies to that WWPN regardless of VSAN. This means that you only have to define a single device alias for any given WWPN, whereas with the fcalias command a different alias needed to be defined for each VSAN.

Using device aliases also provides a couple other key benefits:

    Device aliases are automatically distributed to other Cisco-attached switches. For example, I defined the device aliases on a Cisco MDS 9134 that was attached to the Fibre Channel expansion port of a Cisco Nexus 5010 switch. The Nexus switch automatically picked up the device aliases. As best I can tell, this is controlled by the device-alias distribute global configuration command (or its reverse, the no device-alias distribute, which would disable device alias distribution).
    Once a device alias is defined for a WWPN, anytime the WWPN is displayed the device alias is also displayed. So in the output of various commands like show flogi database, show fcns database, or show zone you will see not only the WWPN, but also that WWPN’s associated device alias.