Jr. Network support here. Looking for a high level answer and nothing too detail.
In regards to Cisco OTV. Let's say datacenter 1 and datacenter 2 have a Nexus 7K at the edge of each location to do the OTV encap and decap.
So now DC1 and DC2 have layer 2 extended between each other. Now the server team that manages the ESX can extend VMs from DC1 to DC2.
If the they take a VM down at DC1 and extend it to DC2, traffic will still route to DC1 and then take layer 2 to DC2. Is that correct?
I can see how this could possible lead to suboptimal "routing" and that's probably where LISP comes in.