< All Cisco CCNA Notes

geraldrbubon | Cisco CCNA | Module 3 - Layer 2 Data Link

By: geraldrbubon | Related Course: Cisco CCNA | Published: June 20, 2016 | Modified: June 20, 2016
Join Cybrary

NotepadLayer 2 DataLink

Layer 2 controls communication on the immediate link between 2 devices

The data is put in a set structure (PDU-Protocol data unit)

Layer 2 addressing scheme is the MAC address 48 bits in length (Hex)

MAC Address
First 24 Bits = OUI Field cannot be changed, vendor specific
Last 24 Bits =
7th most significant bit (2nd on the first 24 bits) = UL Bit Universal Local bit 0ff– address is universally unique, On-means address is assigned locally



NotepadLayer 2 – Mac Addresses

The PDU at layer2 is a FRAME

Dest. MAC -> Source MAC -> Data->Frame Check Sequence FCS houses the CRC – Cyclic Redundancy check

CRC – it performs a calculation on the whole frame and comes up with a number


If Dest and Receiver matches the number, frame is not corrupted or not


< All Cisco CCNA Notes
Join Cybrary

Our Revolution

We believe Cyber Security training should accessible for everyone, everywhere. Everyone deserves the OPPORTUNITY to learn, begin and grow a career in this fascinating field. Therefore, Cybrary is the world's largest community where people, companies and training come together to give everyone the ability to collaborate in an open source way that is revolutionizing the cyber security educational experience.

We recommend always using caution when following any link

Are you sure you want to continue?