Frames and MACs

Lesson 8 of 32 in Coddy's The OSI Model course.

Layer 2 turns raw bits into frames: packages with a source and destination address that make sense on the local network segment.

Those addresses are MAC addresses: burned into every network card at the factory, written as six two-digit hex bytes like 3c:5a:b4:12:34:56. Six bytes is 48 bits, enough that every card ever made gets a unique one.

MACs only matter one hop at a time: your machine to the switch, the switch to the router. Beyond the local segment, layer 3 takes over.

Challenge

Beginner

Two facts about a MAC address: print how many bytes long it is, then how many bits, each on its own line.

Expected output:

6
48

Try it yourself

Terminal

All lessons in The OSI Model

1Why Layers

The Layering Idea Seven Layers Numbers and Names Recap - The Stack

4The Network Layer

IP and TTL Ping and ICMP Routing Tables Recap - Layer Three

7Encapsulation

Wrapping Data Headers Everywhere Reading a Capture Recap - Follow the Wrap

2The Physical Layer

Bits on a Wire How Long Will It Take Duplex and Collisions

5Transport: TCP and UDP

Ports The TCP Handshake TCP vs UDP Sockets in Action Recap - Layer Four

8The Journey of a Packet

A Click Happens Crossing the Networks Arriving and Climbing Recap - End to End

3Data Link and MACs

Frames and MACsReading a MAC ARP Recap - Layer Two

6The Upper Layers

Session and Presentation The Application Layer Watching the Layers Recap - Top of the Stack

Practice on your own: Terminal playground