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Nice maths. Would each router then hold 64TB and doing a lookup per request in that volume of data would be slow

Question: how does dns lookup differ from MAC lookup. Why is domain name lookup feasible, but not MAC?

the router needs to remember where each address goes. with MAC addresses being random, there is no shortcut. DNS is distributed and you look it up one subdomain level at a time, and that can be cached. same for IP, the router only needs to store the subnet for each destination, not all ip addresses.

a central lookup database for mac addresses (which could be distributed by having separate servers for a segment of the address space) doesn't make much sense because the distance of a server to the location of the device is to great and would make updates expensive.

so the router has to remember each address used. but at least it would not have to store all addresses in existence. actually, i think the storage needs are similar to those for NAT. well, except backbone routers which have to store a lot more.

the actual problem is the initial discovery of a MAC address. where does the routing information for a MAC address come from?

you need some peer finding protocols like DHT, and those are slower.

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