22 The Data-Link Layer

What you need to know:

The date-link layer deals with MAC addresses and basic packet transfer between two or more computers connected in the same sort of “network”. It uses the Physical Layer to transfer the packets and is used by the Network Layer in allowing packets to leave the network and reach its final destination.

Medium Access Control (MAC)

Ethernet (IEEE 802.3) also includes some Layer 2 protocols which act as a foundation for general inter-computer communication, this being Medium Access Control or MAC. Every Ethernet-capable NIC (Network Interface Card) has what's called a “MAC address” (sometimes called the “hardware address”), which is set in the hardware. You can change this, but most of the time you do not want to, as this identifies your device for the higher layers. This MAC address takes the form of 12 hexadecimal letters, sometimes in pairs, for example: “12:34:56:78:90:ab” or “aa:aa:aa:aa:aa:aa”.

Get your MAC address on Windows using “ipconfig /all”. Keep in mind it's called “Physical Address” on Windows. Windows also uses dashes instead of colons to separate the pairs, but that is okay.

Get your MAC address on Linux using “ip link”. Ignore the lo option as that is your loop back interface for pinging yourself. Look for an adapter that starts with “enp” or “ens”.

A newer feature of MAC addresses is allocation of 50% of the possible addresses for “private-use”. Google Pixel allows you to use a randomized MAC address on each WiFi you connect to

The first six hex digits is an identifier for the manufacturer of the NIC.

The Network Layer, on Layer 3, which is above this layer uses MAC addresses

How does this relate to Cybersecurity?

MAC addresses are built on the honors’ system. That means that