I have been reading this document on the Nexus 7000 and Catalyst 6500 architectures and designs in a server farm...
(focus on pages 19 to the end).
I am pretty surprised by what I am reading.
I have never configured the Nexus 7000, nor have I deployed any sort of Virtual Switching, but the new design approaches described in this document seem to go completely against the grain of what Cisco has been peddling for the last 5 years or so.
When it comes to the Cisco hierarchical model, I have read many Cisco documents touting the benefits of minimizing and mitigating the L2 domain, maximizing L3 isolation, migrating the access layer to a routed one, leveraging route summarization, stub routing, ECMP, deploying services in the aggregation layer, leaving the core to do nothing but high speed L3 switching with all the route policies and filtering left to the aggregation layer...etc.
Now, in this document, there are recommendations to move the L2/L3 boundry all the way up to the core! Switching in the core? STP in the core? There is talk in the document of the need to sometimes span a VLAN across the entire data center and doing so by migrating the L2 domain to the core. Confusingly enough, it then goes on to mention the drawbacks of doing that (huge fault domains), and as a "solution," recommends creating a separate core layer for each and ever distribution block!
So, the traditional 2-layered distribution block, with L3 uplinks to a core shared across the entire data center is now a 3-layered model, with a separate core layer for each distribution block. The reasoning for this is to span the VLAN across a "zone," which is nothing more than the traditional distribution block. So why couldnt I just span the VLAN using the 2-layered distribution block, as always...and use a shared core?
This document is confusing and reads a lot more like sales and marketing than engineering....
Would love to hear some thoughts.