Media Access Control (MAC) Sublayer of the OSI Data Link Layer by Anthony Sequeira

The Media Access Control (MAC) sublayer of the OSI Data Link layer of th OSI model includes the following chracteristics:

Physical Addressing

A common example of a Layer 2 address is a MAC address, which is a 48-bit address assigned to a device's network interface card (NIC). MAC addresses are written in hexadecimal notation (for example58:55:ca:eb:27:83). The first 24 bits of the 48-bit address are the vendor code. The IEEE Registration Authority assigns a mamufactirer one or more unique vendor codes. You can use the list of vendor codes at to identify the manufacturer of a networking device, based on the first half of the device's MAC address. The last 24 bits of a MAC address are assigned by the manufacturer, and they act as a serial number for the device. No two MAC addresses in the world should have the same value.

Logical Topology

Layer 2 devices view a network as a logical topology. Examples of logical topologies include bus and ring topologies.

Method of Transmitting on the Media

With several devices connected to a network, there needs to be some strategy when a device sends on the media. Otherwise, multiple devices might send at the same time and interfere with one another's transmission.

About The Author

Anthony Sequeira, CCIE No. 15626, is a Cisco Certified Systems Instructor (CCSI) and author regarding all levels and tracks of Cisco Certification. Anthony formally began his career in the information technology industry in 1994 with IBM in Tampa, Florida. He quickly formed his own computer consultancy, Computer Solutions, and then discovered his true passion-teaching and writing about Microsoft and Cisco technologies. Anthony joined Mastering Computers in 1996 and lectured to massive audiences around the world about the latest in computer technologies. Mastering Computers became the revolutionary online training company, KnowledgeNet, and Anthony trained there for many years. Anthony is currently pursuing his second CCIE in the area of Security and is a full-time instructor for the next-generation of KnowledgeNet, Anthony is also a VMware Certified Professional.

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