What are people doing for typical Datacentre designs these days?
Is it a 2 layer or 3 layer model? or is it just spine and leaf?
What about dual connecting servers using LACP etc? would they just have the 2 TOR leaf switches in a vpc then create a port channel to the 2 TOR switches?
Are people doing L3 to the TOR leaf switches or still doing that in the spines?
What about the Core layer etc?
if cisco based design, the ACI - spine and leaf makes life easy, if you looking to build green filed, if you looking to upgrade, still you can connect old network to ACI.
i do not believe investing on FEX waste of investment in the new era, Nexus 9K will be same costing model.
So, is there no core switch anymore ?
is it just spine and leaf with no core?
what dictates the number of spines you should have ?
Have a look at this white paper. There is a section about leaf and spine switches that support ACI.
additional to oher post in case you like to read and connect exiting infrastructure to ACI.