Tim Hieu Ve Ccna

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CCNA Semester 3

Chapter 1: LAN Design

CCNA Exploration 4.0


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Objectives

Describe how a hierarchical network supports the voice,and data needs of a small- or medium-sized business.

Describe the functions of each of the three levels of thehierarchical network design model, the principles ofhierarchical network design (aggregate connectivity,network diameter, and redundancy), and the concept of a

converged network.

Provide examples of how voice and video over IP affectnetwork design.

Select appropriate devices to operate at each level of thehierarchy, including voice and video components.

Match the appropriate Cisco switch to each layer in the

hierarchical network design model.


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Switched LAN Architecture


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The Hierarchical Network Model

Access Layer: interfaces with end devices, to provide ameans of connecting devices to the network and controllingwhich devices are allowed to communicate on the network.

Include routers, switches, bridges, hubs, and wirelessaccess points.

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Distribution Layer: aggregates the data; controls the flow ofnetwork traffic. Distribution layer switches are typically high-performance

devices that have high availability and redundancy to

ensure reliability.5


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Core layer: the high-speed backbone of the internetwork.The core layer is critical for interconnectivity betweendistribution layer devices, so it is important for the core to be

highly available and redundant. The core aggregates thetraffic from all the distribution layer devices, so it must becapable of forwarding large amounts of data quickly.

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The logical representation makes it easy to see whichswitches perform which function. It is much harder to seethese hierarchical layers when the network is installed in a

business.77


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Benefits of a Hierarchical Network

Scalability Hierarchical networks can be expanded easily

Redundancy Redundancy at the core and distribution level ensure path availability

Performance Link aggregation between levels and high-performance core and

distribution level switches allow for near wire-throughout the network

Security

Port security at the access level and policies at the distribution levelmake the network more secure

Manageability Consistency between switches at each level makes management

more simple Maintainability

The modularity of hierarchical design allows the network to scalewithout becoming overly complicated

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Hierarchical Network Design Principles

Network Diameter: Measure the number of devices that a packet has to cross

before it reaches its destination. Keeping the networkdiameter low ensures low and predictable latency

between devices.9


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Bandwidth Aggregation: Bandwidth aggregation is the practice of considering the

specific bandwidth requirements of each part of the hierarchy.

Link aggregation allows multiple switch port links to becombined so as to achieve higher throughput betweenswitches. Cisco has a proprietary link aggregation technologycalled EtherChannel, which allows multiple Ethernet links to be

consolidated.

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Redundancy:

Is one part of creating a highly available network.Redundancy can be provided in a number of ways. Forexample, you can double up the network connectionsbetween devices, or you can double the devicesthemselves.

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Start at the Access Layer

Design a new network: Design requirements, such as the level ofperformance or redundancy necessary, are determined by the business

goals of the organization. Once the design requirements aredocumented, the designer can begin selecting the equipment andinfrastructure to implement the design.

When you start the equipment selection at the access layer, you can

ensure that you accommodate all network devices needing access to thenetwork. After you have all end devices accounted for, you have a betteridea ofhow many access layer switches you need. The number ofaccess layer switches, and the estimated traffic that each generates,

helps you to determine how many distribution layer switches are requiredto achieve the performance and redundancy needed for the network.After you have determined the number of distribution layer switches, youcan identify how many core switches are required to maintain theperformance of the network.

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Converged Network

Small and medium-sized businesses: run voice and video services onthe data network. So how voice and video over IP (VoIP) affect ahierarchical network:

Legacy Equipment

Convergence: voice and video communications on a data network. Converged networks: only feasible in large enterprise organizations.

Convergence: high network costs. Converged networks also required extensive management in relationto Quality of Service (QoS).

Legacy equipment hinders the process.

Most telephone companies today have made the transition to digital-based switches. However, there are many offices that still use analogphones, so they still have existing analog telephone wiring closets.

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Converged Network

Advanced Technology

Convergence is now easier to implement and manage, andless expensive to purchase.

Cisco Catalyst Express 500 switches and a Cisco 7906Gphone suitable for small to medium-sized businesses.

If the business already invested in separate voice, video,

and data networks, it is difficult to abandon an investmentthat still works, but there are several advantages:

One network to manage

Lower implementation and management costs

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Converged Network

New Options:

Converged networks give you options that had not existedpreviously.

Tie voice and video communications directly into anemployee's personal computer system.

You can accomplish the same function using special

software integrated with a personal computer. Softphones,such as the Cisco IP Communicator, offer a lot of flexibilityfor businesses.

With the addition of inexpensive webcams,videoconferencing can be added to a softphone.

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Converged Network

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Converged Network

Separate Voice, Video and Data Networks

Activity: 1.1.3.317


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Matching Switches

to Specific LAN Functions

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Considerations for Hierarchical Network

Switches

Traffic Flow Analysis The process to measure the bandwidth usage on a network and

analyze the data for the purpose of performance tuning, capacityplanning, and making hardware improvement decisions.

Done using traffic flow analysis software. Analyzing the various traffic sources and their impact on the network,

allows you to more accurately tune and upgrade the network toachieve the best possible performance.

Traffic Flow Tools: many tools For a list of some commercial traffic flow collection and analysis tools,

visithttp://www.cisco.com/warp/public/732/Tech/nmp/netflow/partners/commercial/index.shtml.

For a list of some freeware traffic flow collection and analysis tools,visithttp://www.cisco.com/warp/public/732/Tech/nmp/netflow/partners/freeware/index.shtml.

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Switches

User Communities Analysis:

The process of identifying various groupings of users and theirimpact on network performance. The way users are groupedaffects issues related to port density and traffic flow, which, inturn, influences the selection of network switches.

Future Growth20


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Switches

Data Stores and Data Servers Analysis Analyzing traffic on a network: consider the location of servers.

Data stores can be servers, storage area networks (SANs),network-attached storage (NAS), tape backup units, or anyother device or component where large quantities of data arestored.

Client-server traffic and server-server traffic.

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Switches

Topology diagram:

Is a graphical representation of a network infrastructure Shows how all switches are interconnected, any redundant

paths or aggregated ports between switches, devicedensities and user communities.

Allows to visually identify potential bottlenecks

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Switch Features

Switch Form Factors: fixed configuration or modular configuration

stackable or non-stackable

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Switch Features

Performance

Post Density Forwarding Rates Link Aggregation

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Switch Features

Power over Ethernet (PoE): Allows the switch to deliver power to a device over the

existing Ethernet cabling.

Allows you more flexibility when installing wireless accesspoints and IP phones because you can install themanywhere you can run an Ethernet cable.

Layer 3 Functions: Layer 3 switches offer advanced functionality that will bediscussed in greater detail in the later chapters of thiscourse. Layer 3 switches are also known as multilayer

switches.

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Switch Features

Layer 3 Functions

Power over Ethernet

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Switch Features in a Hierarchical Network

Access Layer Switch Features

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Distribution Layer Switch Features

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Core Layer Switch Features

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Switches for SMB

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Switches for SMB

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Switches for SMB

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S i h f SMB


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Switches for SMB

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S it h f SMB


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Switches for SMB

Activity 1.2.4.2 Activity 1.2.4.3

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Summary

The hierarchical design model improves upon the limitation of flat,partial mesh, and mesh design models by improving the performance,scalability, availability, manageability, and maintainability of thenetwork.

Hierarchical network topologies facilitate network convergence byproviding the performance necessary for voice and video data to becombined onto the existing data network.

Traffic flow, user communities, data stores and server location, andtopology diagram analysis can be performed to help identify networkbottlenecks.

The bottlenecks can then be addressed to improve the performance

of the network and accurately determine appropriate hardwarerequirements to satisfy the desired performance of the network.

Cisco switches combine specific form factors, performance, PoE, andLayer 3 support that support the levels of the hierarchical network

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Summary

VLANs separate broadcast domains on switches. VLANs improve network performance, management, and security. VLAN can be used for data, voice, network protocol and network

management traffic.

There are 3 different membership modes: Static, Dynamic, and VoiceVLAN mode.

Routers or Layer 3 switches are required for inter-VLAN communication. Trunks allow multiple VLANs to traverse a single link to simplify intra-

VLAN communication across multiple switches.

IEEE 802.1Q is the standard trunking protocol 802.1Q uses a process of frame tagging to keep VLAN traffic separate as

it traverse the trunk link.

802.1Q does not tag native VLAN traffic, which can result in problemswhen trunking is misconfigured.

Tim Hieu Ve Ccna

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