IP address and Mac address: what are they for?

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Pau Monfort
IP address and Mac address: what are they for?

Brief analysis of two tools we use on a daily basis

If you have to send a letter, you need it the address of the recipient. The address is used to communicate to the postman the place where the letter will be delivered, so the address must be unique. Two houses cannot have the exact same address, otherwise there would be confusion.

The Internet works just like the postal service: instead of sending letters, devices send "data packets", and IP and MAC addresses they determine the route those same packages must take.

What is an IP address?

Un IP address is a unique set of digits that identifies a device connected to the Internet. To understand where this address comes from, we need to understand how the Internet works.

In simple terms, the Internet is a group of separate networks connected together. Each network is called Internet Service Provider (ISP), and if you buy a subscription from an ISP (such as InformaticsKings) you connect to that ISP's network, and to all other networks connected to the ISP.

Each ISP has a pool of IP addresses to manage, and when you sign up for a subscription, you are assigned one. When you receive data from the Internet, the ISP's network sees that your unique IP address is the destination and then routes the data.

There are two types of IP addresses:

- IPv4, i.e. four digits separated by periods, with each digit between 0 and 255 (e.g .:

- IPv6, eight groups of four characters each separated by colons, with each string containing numbers and lowercase letters.

Although there are 4 billion possible addresses that use IPv4,3, they are basically all busy and running out. This is why the entire planet is migrating to IPv6, which delivers up to 320 eleven million of IPv6 addresses.

What is a MAC address?

Un MAC address identifies a unique network interface present on a device. While IP addresses are assigned by ISPs and can be reassigned when devices are plugged in and unplugged, MAC addresses are tied to a physical adapter and are assigned by manufacturers.

A MAC address is a 12-digit string where each digit can be any number from 0 to 9, or a letter between A and F. For better readability, the string is divided into parts. There are three common formats, of which the first is the most common and preferred:

1) 68:7F:74:12:34:56

2) 68-7F-74-12-34-56

3) 687.F74.123.456

The first six digits (the "prefix") represent the adapter manufacturer and the last six the unique identification number for that specific adapter. The MAC address does not contain any information on which network a particular device is connected to.

How do IP and MAC addresses work together?

The IP address it is used to carry data from one to another network using the TCP / IP protocol. The MAC address it is used to bring data to the correct device on a network.

A practical example: suppose your name is "John Smith", which is not sufficiently unique as an identifier. What if we added genealogical information (ie, your "producer")? You would be "Mario Rossi, son of Giorgio, son of ...", going back far enough in time it would become sufficiently unique. This would represent your MAC address.

If I wanted to send you a package, I certainly could not say to the post office "Send it to Mario Rossi, son of Giorgio, son of ...", because it would also take the home address anyway. But even that is not enough: I need your home address and your name, otherwise you will receive the package but you will not know if it was intended for you or your wife. The IP address says WHERE are you, the MAC address instead CHI know.

In other words: your modem / router has a unique IP address ("home address") assigned by your ISP ("post office"). The devices connected to the modem or router ("those living at home") have unique MAC addresses ("personal names"). The IP address carries the data to the router / modem ("mailbox") and then the modem / router forwards it to the correct device ("the recipient").

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