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ITE PC v4.0 Chapter 1

Chapter 4: Switched Networks
Routing and Switching Essentials v6.0

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
1
Cisco Networking Academy Program
Routing and Switching Essentials v6.0
Chapter 4: Switched Networks

Chapter 4 – Sections & Objectives
4.1 LAN Design
Explain how switched networks support small to medium-sized businesses.
Explain how data, voice, and video are converged in a switched network.
Describe a switched network in a small to medium-sized business.
4.2 The Switched Environment
Explain how Layer 2 switches forward data in a small to medium-sized LAN.
Explain how frames are forwarded in a switched network.
Compare a collision domain to a broadcast domain.

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
2

4.1 LAN Design

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
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Cisco Networking Academy Program
Routing and Switching Essentials v6.0
Chapter 4: LAN Design

Converged Networks
Growing Complexity of Networks
Our digital world is changing.
Information must be accessed from anywhere in the world.

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
4
4.1 – LAN Design
4.1.1 – Converged Networks
4.1.1.1 – Growing Complexity of Networks

Converged Networks
Elements of a Converged Network
To support collaboration, networks employ converged solutions.
Data services include voice systems, IP phones, voice gateways, video support, and video conferencing.
Call control, voice messaging, mobility, and automated attendant are also common features.
Multiple types of traffic; only one network to manage.
Substantial savings over installation and management of separate voice, video, and data networks.
Integrates IT management.

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
5
4.1 – LAN Design
4.1.1 – Converged Networks
4.1.1.2 – Elements of a Converged Network

Converged Networks
Cisco Borderless Networks
A network architecture that allows organizations to connect anyone, anywhere, anytime, and on any device securely, reliably, and seamlessly.
Designed to address IT and business challenges, such as supporting the converged network and changing work patterns.

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
6
4.1 – LAN Design
4.1.1 – Converged Networks
4.1.1.3 – Cisco Borderless Networks

Converged Networks
Hierarchy in the Borderless Switched Network
Borderless switched network design guidelines are built upon the following principles:
Hierarchical
Modularity
Resiliency
Flexibility

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
7
4.1 – LAN Design
4.1.1 – Converged Networks
4.1.1.4 – Hierarchy in the Borderless Switched Network

Converged Networks
Access, Distribution, and Core Layers

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
8
4.1 – LAN Design
4.1.1 – Converged Networks
4.1.1.5 – Access, Distribution, and Core Layers

Switched Networks
Role of Switched Networks
Switching technologies are crucial to network design.
Switching allows traffic to be sent only where it is needed in most cases, using fast methods.
A switched LAN:
Allows more flexibility
Allows more traffic management
Supports quality of service, additional security, wireless, IP telephony, and mobility services

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
9
4.1 – LAN Design
4.1.2 – Switched Networks
4.1.2.1 – Role of Switched Networks

Switched Networks
Form Factors
Fixed
Configuration
Switches

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
10
4.1 – LAN Design
4.1.2 – Switched Networks
4.1.2.2 – Form Factors

Switched Networks
Form Factors
Modular
Platform

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
11
4.1 – LAN Design
4.1.2 – Switched Networks
4.1.2.2 – Form Factors

Switched Networks
Form Factors
Stackable
Configuration
Switches

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
12
4.1 – LAN Design
4.1.2 – Switched Networks
4.1.2.2 – Form Factors

4.2 The Switched Environment

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
13
Cisco Networking Academy Program
Routing and Switching Essentials v6.0
Chapter 4: Introduction to Switched Networks

Frame Forwarding
Switching as a General Concept in Networking and Telecommunications
A switch makes a decision based on ingress and a destination port.
A LAN switch keeps a table that it uses to determine how to forward traffic through the switch.
Cisco LAN switches forward Ethernet frames based on the destination MAC address of the frames.

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© 2008 Cisco Systems, Inc. All rights reserved.
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14
4.2 – The Switched Environment
4.2.1 – Frame Forwarding
4.2.1.1 – Switching as a General Concept in Networking and Telecommunications

Frame Forwarding
Dynamically Populating a Switch MAC Address Table
A switch must first learn which devices exist on each port before it can transmit a frame.
As a switch learns the relationship of ports to devices, it builds a table called a MAC address or content addressable memory (CAM) table.
CAM is a special type of memory used in high-speed searching applications.
The information in the MAC address table is used to send frames.
When a switch receives an incoming frame with a MAC address that is not found in the CAM table, it floods it to all ports, except the one that received the frame.

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
15
4.2 – The Switched Environment
4.2.1 – Frame Forwarding
4.2.1.2 – Dynamically Populating a Switch MAC Address Table

Frame Forwarding
Switch Forwarding Methods

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© 2008 Cisco Systems, Inc. All rights reserved.
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16
4.2 – The Switched Environment
4.2.1 – Frame Forwarding
4.2.1.3 – Switch Forwarding Methods

Frame Forwarding
Store-and-Forward Switching
Allows the switch to:
Check for errors (via FCS check)
Perform automatic buffering
Slower forwarding process

Frame Forwarding
Cut-Through Switching
Allows the switch to start forwarding in about 10 microseconds
No FCS check
No automatic buffering

Switching Domains
Collision Domains
Ethernet switch port:
Operating in half duplex, each segment is in its own collision domain.
Operating in full duplex eliminates collisions.
By default, will auto-negotiate full duplex when the adjacent device can also operate in full duplex.

Collision domain – Segment where devices compete to communicate.

Switching Domains
Broadcast Domains
A broadcast domain is the extent of the network where a broadcast frame can be heard.
Switches forward broadcast frames to all ports; therefore, switches do not break broadcast domains.
All ports of a switch, with its default configuration, belong to the same broadcast domain.
If two or more switches are connected, broadcasts are forwarded to all ports of all switches, except for the port that originally received the broadcast.

Switching Domains
Alleviating Network Congestion
Switches help alleviate network congestion by:
Facilitating the segmentation of a LAN into separate collision domains.
Providing full-duplex communication between devices.
Taking advantage of their high-port density.
Buffering large frames.
Employing high-speed ports.
Taking advantage of their fast internal switching process.
Having a low, per-port cost.

4.3 Chapter Summary

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© 2008 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
22
Cisco Networking Academy Program
Routing and Switching Essentials v6.0
Chapter 4: Introduction to Switched Networks

The trend in networks is towards convergence using a single set of wires and devices to handle voice, video, and data transmission.
There has been a dramatic shift in the way businesses operate.
There are no physical offices or geographic boundaries constraints. Resources must now be seamlessly available anytime and anywhere.
The Cisco Borderless Network architecture enables different elements, from access switches to wireless access points, to work together and allow users to access resources from any place, at any time.
The traditional, three-layer hierarchical design model divides the network into core, distribution, and access layers, and allows each portion of the network to be optimized for specific functionality.
It provides modularity, resiliency, and flexibility, which provides a foundation that allows network designers to overlay security, mobility, and unified communication features.
Switches use either store-and-forward or cut-through switching.
Every port on a switch forms a separate collision domain allowing for extremely high-speed, full-duplex communication.
Switch ports do not block broadcasts and connecting switches can extend the size of the broadcast domain, often resulting in degraded network performance.

Chapter Summary
Summary

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