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Reading a MAC

Lesson 9 of 32 in Coddy's The OSI Model course.

A MAC address has structure. The first three bytes are the OUI (Organizationally Unique Identifier): a vendor prefix assigned to the manufacturer. The last three bytes are the card's serial within that vendor.

That makes MACs surprisingly informative: seeing 3c:5a:b4 on an unknown device tells you who built its network card, which is a real technique for identifying mystery devices on a Wi-Fi network.

One special MAC to know: ff:ff:ff:ff:ff:ff, the layer 2 broadcast, received by every device on the segment.

Challenge

Beginner

A device reports the MAC 3c:5a:b4:12:34:56. Print its OUI (the vendor prefix), colons included.

Expected output:

3c:5a:b4

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 MACARP 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