many people have big, flat layer two networks... e.g. one subnet might span locations. Now, personally, I think this is a bad idea in nearly all cases, but many other people disagree with me.
The thing is, vendors of expensive MPLS gear like to sell this idea of 'location independent subnets' to upper management as a way to 'simplify' the network.
Now maybe it's just 'cause I don't know layer two well, but god damn it is so much easier to troubleshoot layer three problems than to troubleshoot layer two problems, so I strongly favor making the subnets location and/or rack dependent.
The very idea makes the network engineer in me cringe. There are so many good reasons to establish layer 3 boundaries before crossing any relatively low speed or high latency connections.
The thing is, vendors of expensive MPLS gear like to sell this idea of 'location independent subnets' to upper management as a way to 'simplify' the network.
Now maybe it's just 'cause I don't know layer two well, but god damn it is so much easier to troubleshoot layer three problems than to troubleshoot layer two problems, so I strongly favor making the subnets location and/or rack dependent.