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Why couldn’t MAC addresses be used instead of IPv4|6 for networking?

If physical address or Mac address is unique why do we need logical addressing?

This because the size and format of Mac address or physical address is different and logical address size and format is same

(The above quotes are from Forouzan's DCN book)

or is there any other reason to it?

  • 2
    This site is for server/networking/... professionals, which involves some (atleast basic) knowledge of networking and routing, and knowing why there is no way to route packets without a hierarchical addressing scheme (logical scheme). Otherwise we could just assign a random number to each postbox (number depending on the postbox vendor), and let the postman figure out where that postbox is, to deliver mail to it.
    – mulaz
    Dec 5, 2012 at 13:34
  • It's getting downvoted (I assume) because of the first reason on the downvote tooltip - This question does not show any research effort. I'd be absolutely shocked if any of the downvoters (or viewers, for that matter) don't actually know the answer to your question. Dec 5, 2012 at 13:34

2 Answers 2


Basically, so that you can communicate with another computer without having to broadcast to every machine on the internet to find out where a given MAC address actually is (and thus, what route to take to get traffic to it).

Two MAC addresses with only the last octet different could be on different sides of the planet, whereas two IPs on the same subnet lie behind the same network device, and thus, with logical addressing it's possible to actually send traffic where it needs to go without having to ask every device on the internet.

  • Oh yeah, and MAC addresses aren't unique either. Dec 5, 2012 at 13:45
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    @MichaelHampton This is true, but they're supposed to be. Well, uniqueish, at least. And even if they were unique, we'd need logical addressing, though. Dec 5, 2012 at 13:49

This is by design. Physical address size and format differs from one link-level technology to another. Network layer protocols, such as IP, can transfer data between two hosts even if they actually use different link-level protocols.


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