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Why do LANs use MAC addressing instead of IP addressing?

In other words, why can't a network just assign an IP address to a local area network device and send the data to that, instead of the MAC address? MAC addresses seem quite redundant without understanding its function.

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    How many times does this have to be asked? You don't understand the purpose of MACs but automatically conclude they're unnecessary? – Ricky Jun 13 '16 at 18:39
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You need to understand the network layers. They are independent of each other. Ethernet and IPv4 are currently the dominant protocols, but that was not always the case, and IPv4 is being replaced with IPv6, which has very different addressing. Layer-2 protocols can carry many different layer-3 protocols, and layer-3 protocols don't care which layer-2 protocol is used. You could ask the same thing of layer-4. Some layer-4 protocols have addresses. In TCP and UDP, these are called ports.

LANs are layer-2 broadcast domains. There are multiple layer-2 protocols, some use 48- bit MAC addresses, some use 64-bit MAC addresses, and some do something else altogether.

LANs can carry a variety of layer-3 protocols, IPv4 is only one of those. If the layer-2 devices need to be specific to a particular layer-3 protocol, it becomes a problem. If you had switches which used IPv4, what happens when you need to add IPv6 devices?

In the past, IPX was the layer-3 protocol of choice for LANs. If switches were designed for IPX, IPv4 may not have come to the fore for the layer-3 protocol. That would have caused a complete overhaul of LAN devices. Since a layer-2 protocol can carry any number of layer-3 protocols, even at the same time, IPv4 could use the same equipment. That is happening now as IPv6 is being rolled out. You can run both IPv4 and IPv6 with the same LAN equipment.

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  • This answer is not helpful, and I'm trying to figure out why. I think you took more time to say what you knew then put thoughtful time into teaching, which clouds what could have been a clear explanation. – Andy Ray May 5 at 3:23
  • I'm sorry you did not find it helpful, but others, including the OP did. You can ask your own question, but there are several here on this subject. – Ron Maupin May 5 at 3:29
  • @AndyRay the fact is this site is not at all about teaching. It is about questions by network professionals for network professionals in real networks. – JFL May 8 at 13:15
  • @JFL we all know that this site is for professionals, but your pleasure of showing your knowledge by down looking others is visible. If we all start to act like this SO will soon self implode, a trend which I already see. I love that fact that 10 years ago these "veterans" used to get upvotes for embarrassing easy questions and now they want to seem unapproachable. – Alexandru-Mihai Manolescu Sep 18 at 20:11
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MAC addresses are a low level component of an Ethernet network (and some other similar standards, such as WiFi). They allow a device to communicate with a machine on the local physical network (LAN), and cannot be routed across the Internet - because a physical hardware might in theory be plugged in anywhere in the world. MAC addresses are at Layer 2 - the data-link layer. MAC Addresses are stored in your arp table(On your PC, on command line: type "arp -a").

On the contrary, IP addresses cover the whole internet. Routers use IP to figure out where to route data. IP aren't helpful in interfacing with the physical hardware on your local network. IPs are found at Layer3 - Network layer. IP are stored in your routing table(On your PC, on command line: type "route -n" or "route print").

For better understanding, I'd strongly advise you to read on the OSI model.

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    "For better understanding, I'd strongly advise you to read on the OSI model" IMO the OSI model confuses more than it helps, it really isn't a good fit. – Peter Green Jun 12 '16 at 23:14
  • This doesn't address the question at all :( – Andy Ray May 5 at 3:25
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LAN uses IP addressing externally to interconnect with other LAN's and point to point links, and internally They use mac addresses to locate the devices that makes up the LAN itself, the mac adress is hardwired like an ID number and has no relative position in the external scheme ,hence the ARP usage and the level 2 OSI reference.

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