CCNA3_M5_Switches (1130763)

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CCNA – Semester3Module 5SwitchesObjectives••••Four major goals of LAN designSteps in systematic LAN designThree-layer design modelList Cisco three-layer switches and their featuresLAN DesignLAN Design Goals• Design goals in most network include:––––FunctionalityScalabilityAdaptabilityManageabilityLAN Design Goals: Functionality• The network must work.• It must allow users to meet their jobrequirements.• The network must provide user-to-user anduser-to-application connectivity withreasonable speed and reliability.LAN Design Goals: Scalability• The network must be able to grow.• The initial design should grow without anymajor changes to the overall design.LAN Design Goals: Adaptability• The network must be designed with an eyetoward future technologies.• It should include no element that wouldlimit implementation of new technologiesas they become available.LAN Design Goals: Manageability• The network should be designed tofacilitate network monitoring andmanagement to ensure ongoing stability ofoperation.LAN design considerations• To maximize available LAN bandwidth andperformance, the following LAN designconsiderations must be addressed:––––The function and placement of serversCollision detection issuesSegmentation issuesBroadcast domain issuesThe 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 email 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.Server placementBandwidth Domain••A bandwidth domain is associated with one port on abridge or switch.In the case of an Ethernet switch, a bandwidth domainis also known as a collision domain.Systematic steps1.

Gathering the users' requirements andexpectations2. Analyzing requirements3. Designing the Layer 1, 2, and 3 LANstructure (that is, topology)4. Documenting the logical and physicalnetwork implementationAvailability requirements• Availability measures the usefulness of thenetwork. Factors that may affect availability:– Throughput– Response time– Access to resources• Every customer may have a distinctdefinition of availability.Analyzing requirements• The next step in designing a network is toanalyze the requirements of the networkand its users.• Network user needs constant change, thenecessity to increase network bandwidthgrows too.Develop LAN topology• LAN topology design can be broken intothe following three unique categories ofthe OSI reference model:– Network layer– Data link layer– Physical layerLAN topologyDocumentation• 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 mapLAN logical mapLAN physical mapCut sheetsVLAN logical mapLayer 3 logical mapAddressing mapsLayer1 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 LANincluding the following elements:– Specify the locations and identification of the MDF and IDF wiringclosets.– Document the type and quantity of cabling used to interconnect theIDFs with the MDF.– Document how many spare cables are available for increasing thebandwidth between the wiring closets.– Provide detailed documentation of all cable runs, the identificationnumbers, and the port the run is terminated on at the HCC or VCC.Typical MDF in star topologyMDF and IDFHCC and VCCExample: Wiring closet locationExample: Rack layout & cable runRack322816UTP18Backbone andServer FarmUTPUTP68HDSLUTP123456789101112131415161718192021222324252627282930313233343536373839404142434445464748UTPPIX FirewallClass Room 18UTPUTPPOWERFAULT DATA ALARMUTPUTP123456789101112131415161718192021222324252627282930313233343536373839404142434445464748UTPUTPUTPClass Room 2UTPRouter 3662123456789101112131415161718192021222324252627282930313233343536373839404142434445464748123456789101112131415161718192021222324252627282930313233343536373839404142434445464748UTPClass Room 3UTPC2924XL - Wg1C2924XL - Wg2UTPUTPUTPUTPUTPMail ServerUTPUTPUTPUTPUTP46UTPUTPUTPExample: Logical DiagramUTPExample: Cable documentationCommon Layer 2 devices• Layer 2 devices provide: flow control, errordetection, error correction, and congestionreduction in the network.• Layer 2 devices determine the size of thecollision domains and broadcast domains.• The two most common Layer 2 devices arebridges and LAN switches.Layer 2 switchUsing router• Allows for segmentation of the LAN intounique physical and logical networks.• Allow for connectivity to wide-areanetworks (WANs), such as the Internet.• Determines traffic flow between uniquephysical network segments based on Layer3 addressing.• Stops broadcasts from reaching other LANsegments.VLAN and broadcast domains• By using VLANs, you can:– limit broadcast traffic to within a VLAN and thuscreate smaller broadcast domains.– provide security by creating the VLAN groupsaccording to function.VLAN communicationVLAN implementationDiagramming a LAN that uses routersDocumentation: Logical network MAPLAN SwitchesLAN design model• Network designs tend to follow one of two generalstrategies: mesh or hierarchical.• In a mesh structure, the network topology is flat, allrouters perform essentially the same functions.• In a hierarchical structure the network is organized inlayers, each of which performs one or more specificfunctions.Hierarchical model• The construction of a LAN that satisfies theneeds of both medium and large-sizedorganizations is more likely to be successful if ahierarchical design model is used.• The use of a hierarchical design model willmake it easier to make changes to the networkas the organization grows.Three layer design• The hierarchical design model includes thefollowing three layers:– The access layer provides users in workgroups access tothe 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 designAccess Layer Overview• The access layer is the entry point for userworkstations and servers to the network.• In a campus LAN the device used at the accesslayer can be a switch or a hub.• Access layer functions also include MAC layerfiltering and microsegmentation, VLANmembership.Access LayerCommon access layer switches• Access layer switchesoperate at Layer 2 andshould be low cost andhigh port density.• The following Ciscoswitches are commonlyused at the access layer:–––––Catalyst 1900 seriesCatalyst 2820 seriesCatalyst 2950 seriesCatalyst 4000 seriesCatalyst 5000 seriesDistribution 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 whichthey occur.–––––Aggregation of the wiring closet connectionsBroadcast/multicast domain definitionVirtual LAN (VLAN) routingAny media transitions that need to occurSecurityDistribution layerDistribution layer switches• The distribution layerswitch must have highperformance.• Switches in this layer arereferred to as multilayerswitches.• The following Ciscoswitches are suitable forthe distribution layer:– Catalyst 2926G– Catalyst 5000 family– Catalyst 6000 familyCore layer overview• The core layer is a high-speed switching backbone.• If they do not have an associated router module, anexternal router is used for the Layer 3 function.• Should not perform any packet manipulation (as ACL).• Provided with redundant alternate paths gives stabilityto the network in the event of a single device failure.• The core can be designed to use Layer 2 or Layer 3switching.

Asynchronous Transfer Mode (ATM) orEthernet switches can be used.Core layerCore layer switches• The following Ciscoswitches are suitable forthe core layer:––––Catalyst 6500 seriesCatalyst 8500 seriesIGX 8400 seriesLightstream 1010Summary• The four major goals of LAN design The steps insystematic 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 distribution layer switches and their features• Cisco core layer switches and their featuresCCNA3 – Module5.

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