It doesn't, prefix lookup is solved faster and cheaper in hardware via CAM or TCAM, maybe combined with hashing, because you can limit yourself to a prefix, dis

It doesn't, prefix lookup is solved faster and cheaper in hardware via CAM or TCAM, maybe combined with hashing, because you can limit yourself to a prefix, discarding the rest of the address. Even if you are right about the endpoints (which only need to know all devices in their specific subtree), as soon as you get to a part of the network where there is no longer just a limited tree below a given router hierarchically, you need a global view of all addresses. This view has to be current, correct and total. That is impossible to achieve, even if the lookup itself would work (which it won't, a conservative estimate of 4 billion active internet devices take up 64GB just for their addresses, not even including routes and metrics). You just cannot search those 64GB fast enough for each packet you are passing through your links (remember, even saturating 10GE in software is hard, and routers do have a lot of those ports in 40 or 100GE...).