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
Mostly because the IP address is structured, so it contains information about which network you’re on. That makes routing possible.
Imagine if we just used MAC addresses. When you visit reddit, their server knows “we need to send a response to this MAC address”
How do the routers along the way know where that is? Do they store a list of *every* MAC address on the internet in their routing tables?
With IP addresses they can just store ranges. “Anything from this IP to that IP are owned by this company, and so should be routed in that direction”, or even “anything in this range is somewhere over in Asia. Let’s send the response in *that* direction first, and let someone else deal with the fine-grained stuff”
With MAC addresses you wouldn’t be able to do that. You’d have to know where every single MAC address is located.
You need conform to established protocols. The MAC address is visible only to directly connected devices on the same network. If you need to cross a router, the data packet will be sent to one if the router’s MAC addresses and be emitted from a port with another MAC address. Think of it like a numbering of mail exchange points that is internal to a postal system vs street addresses.
ELI5 – your Mac address is like your Social Security Number – no matter where you move to it is attached to you (the specific modem, network card, etc.) but people can’t easily look you up by your SSN and you don’t give your SSN out to everyone. Whereas your IP address is like your phone number. Everyone has caller ID nowadays and can see the number that you’re calling from and if you list yourself in the telephone directory (DNS) or stick it on your social media people can easily look up your name (domain address) and get your phone number. You can choose to either keep the same telephone number (Static IP) or change it like a burner phone (Dynamic IP).
MAC is the ‘permanent’ identifier attached to network card of the device
the IP address is a “temporary” identifier of a device that helps the network keep track of what MACs are attached to the it
it ‘s like the MAC is your birth certificate name and the IP would be like a temporary nickname given while you are in a store… then you go to a bar and they give you another temporary nickname/IP…. and so on…
MAC is like your social security number and IP is like your house address you happen to be living at.
Knowing who **you** are does no good when trying to send something to you. You might not necessarily be at home or you might move on a regular basis. So knowing what address you are actually at is necessary to get something to you.
When a manufacturer builds a device intended to be networked, they assign it a MAC address according to a set of conventions. Normally this number is a combination of the manufacturer’s id, the product line id and a sequence number. However, MAC addresses only need to be locally unique so you can set them to (mostly) whatever you like as long as no more than two devices on the local network have the same MAC address.
IP addresses are used to route traffic globally, so they need to be centrally controlled. While consumers will normally have their addresses assigned dynamically by server providers, those service providers normally have a range of IP addresses they can use to receive traffic.
Think of a MAC address as your name
Think of an IP address as your home address or phone number.
Me knowing your name, does not mean I automatically know your phone number or mailing address.
At the same time if I am clever I can use I can use the knowledge of one to figure out the other, but I still wouldn’t put only your name on a letter I am sending you once I have figured out your mailing address and expect it to arrive to you.
Because while I now have the knowledge of where the person going by your name lives, the postal service (rest of the network devices) do not necessarily also all know that information without also having to go and try to look it up.
So to make it easier and faster for everyone I just put your postal address (IP address) instead.
Hopefully that makes sense, it’s not a perfect analogy but it is the most simple way I can explain it.
MAC is also known as a hardware address, its like a serial number for your network card that is unique to your device and unless ‘spoofed’ (faked, I’m looking at you android and apple) it is unchanging.
IP addresses on the other hand are variable and when setting up routing I can tell a router to send all traffic for the 10.1.x.x network to switch A and all traffic for 10.2.x.x to switch B with a single line of code for each (as when IPv4 was put in place memory was at a premium).
Nowadays with IPv6 the MAC is used but only makes up half of the ‘IP’ with the other information serving the same purpose as IPv4 would, allowing devices to know where to send data to 🙂
A MAC address is your legal name. It’s who you are and isn’t easily changeable.
An IP address is a nickname. Some people call you Frank, some people call you Frankie.
Depending on what router (friend group) you’re with, your IP (nickname) will differ.
MAC address is like your street address. 42 Wallaby Way. It’s hard to get directions with just that information. There can be multiple (vendors try to eliminate this per geographic region, but it happens).
If we go with IP, now it’s more like a set of directions for the routers to the MAC. Go to Australia, Go to Sydney, Go to Wallaby Way, Go to 42.
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