I’m aware that the mac address is part of the data link layer, but why can’t I just use my MAC address as IP address, too?
Why do I need both addresses?
In: 14
The MAC address is a specific hardware identifier. It might be more helpful to think of it as the name of the device rather than the address.
The IP address is a location to get to.
If I said “I need this to go to Bill Smith” without any further information, it would be very difficult to get a message to him. However, if I said “I need this to get to the occupant of suite 342 in Generic Fancy Hotel in Singapore,” that would be a pretty good set of instructions which would tell people where they need to go to bring a package to Mr. Smith. His name is Bill Smith regardless of whether he’s sleeping in Singapore, in London, or at home in Ashburn, Virginia, but each of those locations has a different address.
If you’re connecting to something on your laptop at home, and at a hotel on the other side of the world, it’s the same MAC address. However, that MAC address does not have any information on how to get to the recipient.
The laptop will connect to the internet through the network’s outward-facing IP address. Typing in https://www.netflix.com will result in a Domain Name System query: if an IP address for this domain name isn’t already saved in a local cache, it asks the default DNS server where to go. If that DNS server doesn’t have it, it will ask another DNS server, until it either comes up with an answer or decides that it can’t find an answer. With this IP address, the router will consult its routing tables to determine the best router to send your request in order to get a step closer to the destination, until it ultimately gets to Netflix’s network, where they will send your request to a computer called www, which will return a file called main.html to be displayed in your web browser. It will go through the same process of determining a route to get to your internet-facing IP address. Once it gets here, the router and other network devices figure out which MAC address on the network to send main.html to, and then you can click something on main.html to use the same process to request that www send you the Oaxaca episode from the new season of *Somebody Feed Phil* because you want to see a funny guy eat Mexican food for 45 minutes.
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