Who Gets the Frame? — TechKnowSurge

About this interactive

A hub is the simplest way to join devices on Ethernet. Whatever signal comes in on one port, the hub sends out of every other port. It reads nothing and decides nothing. (That is why a hub counts as a Layer 1, physical-layer, device, even though it is Ethernet equipment.) Hubs are rare now, because switches replaced them, but they show how Ethernet works. If every device receives every frame, each one needs a way to tell which frames are for it. That is the MAC address. Every network interface card has one, and every frame is tagged with the MAC address of the device it is for. Each card compares that destination with its own address: a match, and it processes the frame; no match, and it ignores it. A MAC address is 48 bits. Written in binary that is hard to read, so it is shown as 12 hexadecimal digits (each hex digit is 4 bits), usually in pairs separated by colons or dashes. The separators, and upper or lower case, are only for people; the address is the same. Where does it come from? Nobody assigns it on the network. It is a burned-in address, set by the company that made the network card (often not the company that made the computer). Move the card to another computer and the address goes with it. Because every device on a hub receives every frame, software on any one of them could capture traffic meant for the others: one of the security concerns the lesson raises, and one reason switches took over.

What you'll learn

Predict which devices on a hub receive a frame and which one processes it, by reading the frame's destination MAC address
Read a MAC address: 48 bits written as 12 hexadecimal digits, burned into the network card by the card's maker, with separators that are only for display

Aligned to

CompTIA Network+

1.2 Compare and contrast networking appliances, applications, and functions.

1.1 Explain concepts related to the Open Systems Interconnection (OSI) reference model.

CompTIA A+ Core 1

2.2 Compare and contrast common networking hardware.

Cisco CCST Networking

1.1 Identify the fundamental conceptual building blocks of networks

Cisco CCNA

1.13 Describe switching concepts

CompTIA Tech+

1.1 Compare and contrast notational systems.

Key terms

Hub: A basic Layer 1 network device that receives a signal on one port and repeats it out every other port simultaneously, creating a single shared collision domain among all connected devices. Hubs have been replaced by switches in modern networks because they waste bandwidth and cause collisions.
MAC Address: A 48-bit hardware address assigned to a network interface and written as six hexadecimal octets, such as 00:1A:2B:3C:4D:5E. It identifies a device uniquely on a local network segment, and switches forward frames by looking it up in their MAC address table.
Burned-In Address: A MAC address permanently assigned to a network interface card by its manufacturer at the time of production.
Network Interface Card: A hardware component that connects a computer to a network.
Hexadecimal: A base-16 number system using digits 0–9 and letters A–F; each hex digit maps to exactly 4 bits, making it a compact shorthand for representing binary data.

Topics

Hub Mac Address Burned In Address Interactive Predict

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