A server farm in a single broadcast domain should use a shortest way to the next router minimizing inter-switch traffic. Faking Neighbor Discovery messages direct each server to the right router.
Application servers often need to communicate to each other in a common layer2 area. If such an area spans multiple networking devices, the data flow is likely to be inefficient. Various methods exist to solve this problem including expensive SDN technology.
This talk focuses about the low budget solutions. Starting from different static routes per server over partially broken networks (filtering ND and FHRP on the inter switch links) up to faking the whole Neighbor Discovery in the Layer 2 area.