ccna3 m5 switches

8/17/2019 CCNA3 M5 Switches

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CCNA – Semester3

Module 5

Switches

Objectives

• Four major goals of LAN design

• Steps in systematic LAN design

• Three-layer design model

• List Cisco three-layer switches and their features


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LAN Design

LAN Design Goals

• Design goals in most network include:

– Functionality

– Scalability

– Adaptability

– Manageability


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LAN Design Goals: Functionality

• The network must work.

• It must allow users to meet their job

requirements.

• The network must provide user-to-user anduser-to-application connectivi ty with

reasonable speed and reliability.

LAN Design Goals: Scalability

• The network must be able to grow.

• The initial design should grow without any

major changes to the overall design.


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LAN Design Goals: Adaptabil ity

• The network must be designed with an eye

toward future technologies.

• It should include no element that would

limit implementation of new technologiesas they become available.

LAN Design Goals: Manageability

• The network should be designed to

facilitate network monitoring and

management to ensure ongoing stability of

operation.


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LAN design considerations

• To maximize available LAN bandwidth and

performance, the following LAN design

considerations must be addressed:

– The function and placement of servers – Collision detection issues

– Segmentation issues

– Broadcast domain issues

The function and placement of servers

• Servers provide network services such as: file sharing,printing, communication, and application services.

• Each server is dedicated to one function, such as e-mail or file sharing.

• Servers can be categorized into two distinct classes:

– Enterprise servers• Supports all the users on the network (such as e-mail or DNS).

• Should be placed in the main distribution facility (MDF).

– Workgroup servers

• Supports a specific set of users.

• Should be placed in the intermediate distribution facility (IDF)closest to the users accessing them.


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Server placement

Bandwidth Domain

• A bandwidth domain is associated with one port on a

bridge or switch.

• In the case of an Ethernet switch, a bandwidth domain

is also known as a collision domain.


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Systematic steps

1. Gathering the users' requirements and

expectations

2. Analyzing requirements

3. Designing the Layer 1, 2, and 3 LAN

structure (that is, topology)

4. Documenting the logical and physical

network implementation

Availability requirements

• Availability measures the usefulness of the

network. Factors that may affect availabil ity:

– Throughput

– Response time

– Access to resources

• Every customer may have a distinct

definition of availability.


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Analyzing requirements

• The next step in designing a network is to

analyze the requirements of the network

and its users.

• Network user needs constant change, thenecessity to increase network bandwidth

grows too.

Develop LAN topology

• LAN topology design can be broken into

the following three unique categories of

the OSI reference model:

– Network layer

– Data link layer

– Physical layer


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LAN topology

Documentation

• The final step in LAN design methodology is todocument the physical and logical topology of thenetwork.

• Important LAN design documentation includes thefollowing:

– OSI layer topology map – LAN logical map

– LAN physical map

– Cut sheets

– VLAN logical map

– Layer 3 logical map

– Addressing maps


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Layer1 design goals

• Choose cable type.

• Identify work area and HCC.

• Identify MDF, IDF, HCC, VCC and POP.

• Choose Ethernet or Fast Ethernet.• Documentation and physical diagrams.

Logical diagram

• The logical diagram is the basic road map of the LAN

including the following elements:

– Specify the locations and identification of the MDF and IDF wiring

closets.

– Document the type and quantity of cabling used to interconnect theIDFs with the MDF.

– Document how many spare cables are available for increasing the

bandwidth between the wiring closets.

– Provide detailed documentation of all cable runs, the identification

numbers, and the port the run is terminated on at the HCC or VCC.


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Typical MDF in star topology

MDF and IDF


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HCC and VCC

Example: Wiring closet location


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Example: Cable documentation

Common Layer 2 devices

• Layer 2 devices provide: flow control, errordetection, error correction, and congestionreduction in the network.

• Layer 2 devices determine the size of the

collision domains and broadcast domains.• The two most common Layer 2 devices are

bridges and LAN switches.


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Layer 2 switch

Using router

• Allows for segmentation of the LAN into

unique physical and logical networks.

• Allow for connectivity to wide-area

networks (WANs), such as the Internet.• Determines traffic flow between unique

physical network segments based on Layer

3 addressing.

• Stops broadcasts from reaching other LAN

segments.


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VLAN and broadcast domains

• By using VLANs, you can:

– limit broadcast traffic to within a VLAN and thus

create smaller broadcast domains.

– provide security by creating the VLAN groups

according to function.

VLAN communication


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VLAN implementation

Diagramming a LAN that uses routers


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Documentation: Logical network MAP

LAN Switches


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LAN design model

• Network designs tend to fol low one of two general

strategies: mesh or hierarchical.

• In a mesh structure, the network topology is flat, all

routers perform essentially the same functions.

• In a hierarchical structure the network is organized inlayers, each of which performs one or more specific

functions.

Hierarchical model

• The construction of a LAN that satisfies the

needs of both medium and large-sized

organizations is more likely to be successful if a

hierarchical design model is used.• The use of a hierarchical design model wil l

make it easier to make changes to the network

as the organization grows.


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Three layer design

• The hierarchical design model includes the

following three layers:

– The access layer provides users in workgroups access to

the network. – The distribution layer provides policy-based connectivity.

– The core layer provides optimal transport between sites.

The core layer is often referred to as the backbone.

Three layer design


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Access Layer Overview

• The access layer is the entry point for user

workstations and servers to the network.

• In a campus LAN the device used at the access

layer can be a switch or a hub.

• Access layer functions also include MAC layer

fil tering and microsegmentation, VLAN

membership.

Access Layer


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Common access layer switches

• Access layer switches

operate at Layer 2 and

should be low cost and

high port density.

• The following Cisco

switches are commonly

used at the access layer:

– Catalyst 1900 series





Distribution layer overview

• It helps to define and separate the core.

• Policies can be applied and access control lists canfilter packets.

• Isolates network problems to the workgroups in which

they occur. – Aggregation of the wiring closet connections

– Broadcast/multicast domain definition

– Virtual LAN (VLAN) routing

– Any media transitions that need to occur

– Security


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Distribution layer

Distribution layer switches

• The distribution layer

switch must have high

performance.

• Switches in this layer are

referred to as multilayerswitches.


switches are suitable for

the distribut ion layer:

– Catalyst 2926G

– Catalyst 5000 family

– Catalyst 6000 family


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Core layer overview

• The core layer is a high-speed switching backbone.

• If they do not have an associated router module, an

external router is used for the Layer 3 funct ion.

• Should not perform any packet manipulation (as ACL).• Provided with redundant alternate paths gives stability

to the network in the event of a single device failure.

• The core can be designed to use Layer 2 or Layer 3

switching. Asynchronous Transfer Mode (ATM) or

Ethernet switches can be used.

Core layer


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Core layer switches


switches are suitable for

the core layer:



– IGX 8400 series

– Lightstream 1010

Summary

• The four major goals of LAN design The steps in

systematic LAN design

• Design issues associated with Layers 1, 2, 3

• The three-layer design model

• The functions of each layer in the three-layer model

• Cisco access layer switches and their features

• Cisco distr ibution layer switches and their features

• Cisco core layer switches and their features


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CCNA3 – Module5

ccna3 m5 switches

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