I am working on designing the logical topology for a new data center rollout. I'm reading "Cisco Data Center Infrastructure 2.5 Design Guide" and going with the multi-tier design. There are multiple options for this design, including looped layer 2 and loop-free.
The benefit of the looped design, it says, is layer 2 adjacency for servers that require it. The loop-free topology apparently limits layer 2 adjacency "to a single pair of access switches".
I don't quite understand what this means. I would assume it is referring to how many layer 2 "hops" a server is away from another, but in both cases it seems traffic requires a trip up to the aggregation layer (assuming a L2/L3 switch) to cross vlans. If we're talking the same vlan, well looped seems even worse because servers on the same vlan have to traverse up to the agg layer to communicate versus what seems like a trip directly to the connected switch with the loop free example.
Can anyone shed some light on my misunderstanding?