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LAN Design Methodology for Efficient Network Functionality

Explore LAN design considerations for network functionality, scalability, and manageability to meet user requirements. Learn how servers and switches are placed strategically for optimal performance.

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LAN Design Methodology for Efficient Network Functionality

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  1. CCNA 3 v3.1 Module 5

  2. CCNA 3 Module 5 Switches/LAN Design

  3. LAN • Spans a • single room • Building • set of buildings that are close together • Campus • Group of buildings on a site and belong to a single organization

  4. Network Design Requirements • Functionality of the network • It must work with reasonable speed and reliability • It must allow users to meet their job requirements • Scalability of the network • Must be able to grow without any major changes to design • Adaptability of the network • Designed with a vision toward future technologies • Manageability of the network • It should facilitate network monitoring and management to ensure ongoing stability of operation

  5. Why have LANs Expanded • Development of high-speed technologies • E.g., Asynchronous Transfer Mode (ATM) • Complex LAN architectures • LAN switching • Virtual LANs (VLANs)

  6. Design consideration to maximize available LAN bandwidth and performance • The function and placement of servers • Collision detection issues • Segmentation issues • Broadcast domain issues

  7. LAN Servers • Provide • File sharing, Printing, Communication, Application services • Do not function as workstations • Run specialized operating systems • NetWare, Windows NT, UNIX, and Linux • Usually dedicated to one function • E.g., e-mail or file sharing • Categorized into two distinct classes • Enterprise servers • Workgroup servers • Layer 2 LAN switches located in the MDF and IDFs should allocated 100 Mbps to these servers

  8. Enterprise Server • Supports all the users on the network • service that everyone in an organization would need (centralized function) • Offers services such as • e-mail • Domain Name System (DNS) • Placed in the Main Distribution Facility (MDF)

  9. Workgroup Server • Supports a specific set of users • services such as • word processing • file sharing • Print services • Placed in the Intermediate Distribution Facilities (IDFs) • Closest to users accessing the applications

  10. Bridging and Switching • Excessive collisions reduce available bandwidth by 35% or 40% • Segmentation with bridges and switches • Splits 1 collision domain into 2 or more collision domains • Create multiple collision domains • Create a single broadcast domain • Stations can get dedicated bandwidth (microsegmentation) • Broadcast MAC address • FF:FF:FF:FF:FF:FF • Bridges and switches pass broadcast on • Routers filter broadcasts

  11. LAN Design Methodology • Gather requirements and expectations • Identify any current network problems • Information includes • Organization's history • Current status • Projected growth • Operating policies • Management procedures • Office systems and procedures • Viewpoints of the people using the LAN • requirements allow for an informed estimate of costs and timelines for projected LAN design implementation

  12. Availability measures the usefulness of the network and is affected by • Throughput • Response time • Access to Resources • Analyze requirements and data • User requirements constantly change • Increased need for bandwidth due to • voice and video-based network applications • Assess user requirements • LAN must provide prompt and accurate information

  13. Design the Layer 1, 2, and 3 LAN structure • Star topology or Extended Star topology • Use Ethernet 802.3 CSMA/CD technology • LAN topology design can be broken into • Network layer • Data link layer • Physical layer

  14. Document the logical and physical network implementation • Physical topology is the way the various LAN components are connected together • Logical design is the flow of data in a network and the naming and addressing schemes used in the implementation of the LAN design solution. Specify the locations of the MDF and IDF Document the type and quantity of cabling Document spare cables Useful for troubleshooting

  15. LAN Design Documents • OSI layer topology map • LAN logical map • LAN physical map • Cut sheets • VLAN logical map • Layer 3 logical map • Addressing maps

  16. OSI Layer Topology MAPExtended Star Topology in a Multi-campus Building

  17. Cut Sheet • Provide detailed documentation of all cable runs • Identification numbers • Port the run is terminated on at the HCC or VCC

  18. VLAN Logical MAP Communicates between VLANs Group users by department, team or application Provides broadcast containment and security Routers provide communication between VLANs Combines L2 & L3 technology to limit collisions and broadcasts

  19. Layer 3 Logical MAP

  20. Addressing Map Used in troubleshooting

  21. Layer 1 Design • Physical Cabling • Fast Ethernet • 100 Mbps, can be full-duplex • Fiber-optic backbone • Cat 5e UTP horizontal runs • TIA/EIA-568-A specifications

  22. TIA/EIA-568-A • Every device connected to the • network should be linked to a • central location with • horizontal cabling • Main wiring closet MDF • IDF needed for every 100 m • Vertical cable connects • IDF and MDF • (normally fiber cable)

  23. Layer 2 Design • Provide flow control, error detection, error correction, and to reduce congestion in the network • Layer 2 devices are bridges and switches • Provide microsegmentation of the network • Reduces the size of collision domains and reduces collisions • Boost performance for a workgroup or a backbone • Asymmetric Switching can allocate bandwidth on a per-port basis (10-Mbps and 100-Mbps ports ) • Provide more bandwidth to vertical cabling, uplinks, and servers

  24. Asymmetric Switching In a pure switched LAN the size of the collision domain is 2

  25. All hosts connected to the shared LAN hub share the same collision domain and bandwidth

  26. Layer 3 Design • Router is a layer 3 device • create unique LAN segments • dividing networks into subnetworks, or subnets (scalability) • Allow communication between segments based on Layer 3 addressing (IP addressing) • Forwards data packets based on destination addresses • Does not forward LAN-based broadcasts (e.g., ARP requests) • Entry and exit point of a broadcast domain • Stops broadcasts from reaching other LAN segments • Serve as firewalls for broadcasts • Allows for segmentation of the LAN into unique physical and logical networks • Allow for connectivity to wide-area networks (WANs), such as the Internet

  27. Addressing Scheme should be constant throughout the network Physical port is used to implement VLAN assignment VLAN 1 - Ports P1, P4, P6 VLAN 2 – Ports P2, P3, P5 Router allows communication between VLANs

  28. Hierarchical Design Model • Access layer • Connects end users into the LAN (closest to end user) • Host switches • Workgroup servers • Access layer services provides services such as VLAN membership • Distribution layer • Packet manipulation and Interconnecting workgroups • Layer 3 switches • Enterprise servers • Core layer • Provides the fastest connection between the distribution points – no packet manipulation • Backbone • Optimal transport between sites

  29. Hierarchical Design Model

  30. Access Layer • Entry point for user workstations and servers to the network • Access Layer devices are a switch or a hub • Shared bandwidth - Hub • Switched bandwidth - Switch - bandwidth is dedicated • Access layer functions include • MAC layer filtering - direct frames only to the switch port that is connected to the destination device • Microsegmentation – 2 devices in collision domain

  31. Distribution Layer • Provide boundary definition in which packet manipulation can take place • Networks are segmented into broadcast domains • Policies can be applied • Access Control Lists can filter packets • Isolates network problems to workgroups they occur • Prevents these problems affecting the core layer • Operate at Layer 2 and Layer 3 • Functions • Aggregation of the wiring closet connections • Broadcast/multicast domain definition • Virtual LAN (VLAN) routing • Any media transitions that need to occur • Security

  32. The Core Layer • High-speed switching backbone • Interconnects distribution layers • Router is used for the Layer 3 function • Should not perform any packet manipulation • Use Layer 2 or Layer 3 switching • Asynchronous Transfer Mode (ATM) or Ethernet switches can be used

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