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Monthly Archives: January 2015


Device Alias on Cisco MDS

It is definitely not convenient to configure a zone or any CFS application using WWpN.

20:ab:3d:2c:4f:89:fa:ab is not very human readable and it is definitely not efficient to keep traces of the WWpN in your MDS configuration.

Device-alias is a proprietary feature created by Cisco to make your life much easier. It will map an human readable description to WWpN.

Let’s first setup our infrastructure for this blogpost and it’s a rather simple topology, but it sums up what we are trying to achieve:

 

Device_Alias
 

Let’s first setup our VSANS,FCDOMAINS and E ports on both MDS

 

I wanted MDS02 to be our principle switch for both VSANS into our very large fabric. 🙂

 

The JBOD has to be linked with VSAN100 .

 

The Fabric is stable and both VSANS are being forwarded on both trunks.

 

Device-alias has 2 mode of configuration :

  • Basic :  Applications that will use device-aliases like zoning will expand them to regular WWpN.
  • Enhanced:  Applications that will use  device-aliases like zoning will keep track of the alias and will use it in a native format

What does that really mean ? We will configure 2 aliases and 2 zones using both methods and you will be able to check by yourself what does Cisco wanted to achieve.

Let’s check that the whole fabric (2 switches 🙂 ) is in basic device-alias mode:

Now let’s configure the device-alias for the JBOD and for a fictitious initiator

CFS should lock the Fabric from a configuration point of view, no other users would be able to override the configuration unless they clear the lock.

Commit the device-alias is mandatory in order to spread the entries throughout the whole fabric.

As we can see, the Aliases have been synchronized. Now it is time to configure a zone and check how the basic device-alias mode is different than enhanced device-alias mode.

The zoneset needs to be activated (INITIATOR does not have a fcid because it is a fake WWpN and hence the fact that it has not registered to the fabric)

As we can see the active zoneset has both the device-alias and WWpN, same thing happen for the FULL zone

Now let’s add another aliases but with the enhanced mode feature this time. You will see that the enhanced mode can be configured only on one switch in the fabric. It is automatically replicated to all other switches in the fabric using CFS

Device-alias configuration is similar to the one we did previously

The zoneset application should now use the device-alias mode to display the aliases using the native format instead of WWpN

We can now check the final result of our tests:

VSAN100 zoneset is using device-alias in basic mode while VSAN200 zoneset is using enhance mode

It is been a long post and some readers might find it annyoing but I wanted to scrutinize every steps of the configuration to understand how it really works behind the scene.

Please feel free to share your experience or comments.

 Nicolas