LAN Design

1. LAN Design Semester 3, Chapter 4 Allan Johnson

2. Go There! Go There! Go There! Go There! Go There! Table of Contents Design Goals & Components Network Design Methodology Layer 1 Design Layer 2 Design Layer 3 Design

3. Table of Contents End Slide Show Design Goals & Components

4. LAN Design Goals • Critical to design is insuring a fast and stable network that will scale well as the organization grows • Design steps are... • Gather & establish design goals based on user requirements • Determine data traffic patterns now & in the future • Define Layer 1, 2, & 3 devices & the LAN/WAN topologies • Document physical & logical network implementation

5. Establish the Design Goals • Although organizations are unique to the customer, the following requirements tend to be generic to all. The network must have... • Functionality--speed and reliability • Scalability--ability to grow without major changes • Adaptability--easily implements new technologies • Manageability--facilitates monitoring and ease of management

6. Critical Components of LAN Design • With the emergence of high-speed technologies and complex LAN technologies, the following critical components need addressing in design • Function & placement of Servers • Collision Detection • Microsegmentation • Bandwidth v. Broadcast domains

7. Placement of Servers • Servers now perform special functions and can be categorized as either... • Enterprise Servers--supports all users on the network • DNS and mail servers • should be placed in the MDF or... • Workgroup Servers--supports a specific set of users • file serving such as specialized databases • should be place in the IDF closest to users

8. Intranets & Collisions • Intranets are internal to the organization and are not accessible by the public over the Internet. • Intranet Servers use browsers to provide access to authorized users. • This has caused an increase in needed bandwidth. Therefore, design must address... • Type of data to be accessed • Server privileges • Outfitting desktops with faster connectivity • More processing power • 10/100Mbps NICs to provide migration to switched technologies • Collision detection and minimization has become a major concern as users attempt to access the same server. • As we’ve seen, switches can provide dedicated bandwidth to minimize or eliminate collsions.

9. Broadcasts & Segmentation • Layer 2 devices segment collision domains • Layer 3 devices segment broadcast domains

10. Bandwidth v. Broadcast Domains • A bandwidth domain is shared by all devices on a single switched port. • Synonymous with collision domain • A broadcast domain is shared by all devices on a single router interface.

11. Table of Contents End Slide Show Network Design Methodology

12. Gathering & Analyzing Requirements • Gathering data about the organization includes the bullets in the graphic.

13. Network Availability • Network design seeks to provide the greatest availability for the least cost. • Factors that affect availability include... • Throughput • Response time • Access to resources • In the graphic, what type of server is each and where should each be placed?

14. Physical Topologies • In the CCNA curriculum, we concentrate on the star/extended star physical topology which typically uses the Ethernet 802.3 standard. • Why? Because it is the most popular topology used in LANs. • The next three sections, evaluate the extended star by layers.

15. Table of Contents End Slide Show Layer 1 Design

16. Ethernet Cable Runs • The physical cabling (also called the cable plant) is the most important Layer 1 issue to consider when designing a network. • Design issues include... • Type of cable to use (twisted-pair, coax, fiber) • Where to use each type (e.g. fiber on the backbone) • How far each run must travel before being terminated (twisted-pair is limited to what distance?) • In an existing LAN, a cable audit is performed to determine where upgrading and/or replacement of bad cables is needed.

17. MDF & Other 568A Acronyms • Whether the LAN is a star or extended star, the MDF is the center of the star. • From the workstation to the telecommunications outlet, the patch cable should be no more than 3m. • From their to the patch panel, called the HCC, no more than 90m. • From the patch panel (the HCC) to the switch, no more than 6m.

18. MDF & Other 568A Acronyms • When distances to the MDF are more than 100m, an IDF is normally added. • The cable run from the IDF to the MDF is called the VCC and is usually fiber. • VCC is just another name for the backbone. • By adding more wiring closets (more IDFs), you create multiple catchment areas (Click of graphic button) Graphic

19. 10BaseT and 100BaseT Ethernet • 100 BaseT (also called Fast Ethernet) is now the standard for connecting IDFs to the MDF. • Although you can run Fast Ethernet over 100BaseT cabling (twisted pair), the distance limitation means fiber is most often used • The 100BaseT standard running on twisted pair is called 100BaseTX • On fiber, it is called what? • What is Gigabit Ethernet called?

20. Layer 1 Logical Documentation • Layer 1 logical documentation is concerned with... • exact location of MDF/IDF • type & quantity of cabling • room locations & # of drops • port numbers • cable labels • Notice Layer 1’s logical documentation shows nothing about logical addressing • The Logical Diagram and Cut Sheet are primary tools for design, but are crucial to the tech who is troubleshooting.

21. Table of Contents End Slide Show Layer 2 Design

22. Common Layer 2 Devices • The two most common Layer 2 devices are... • Bridges and • LAN Switches • Both provide the added benefit of what? • Segmenting collision domains into microsegments. • Switches can also provide connections of unlike bandwidth (e.g., 100Mbps to the server & 10Mbps to workstations). This is called...?

23. Sizing Collision Domains • In a switched LAN environment using hubs, the bandwidth of each switched port is shared by all the devices. Therefore, they also share the same collision domain. • To determine the bandwidth per host, simply divide the port’s bandwidth by the number of hosts (see graphic). • In a pure switched LAN environment where each host has its own port, the size of the collision domain is 2. If running full-duplex, then the collision domain is eliminated. Why?

24. Migrating to 100BaseT • As long as your workstations all have 10/100 NICs, increasing the bandwidth is easy. • Replace the hub with a 100Mbps capable hub and patch the HCC into a 100Mbps port on the switch. • In addition, you can add another 100Mbps VCC from the IDF to the MDF, which provide 200 Mbps to the IDF’s switch. • In the graphic, the red lines represent migrating to 100Mbps.

25. Table of Contents End Slide Show Layer 3 Design

26. Routers and Design • Routers provide both physical and logical segmentation. • Physically, routers segment what? • Logically, routers segment according to Layer 3 addressing dividing the LAN into logical segments called subnets.

27. VLANs & Broadcast Domains • As we learned in Chapter 3, VLAN capable switches help routers contain broadcasts. • The graphic shows two broadcast domains. • Notice there is also two subnets. How do we know that? • The router provides communication between the two VLANs.

28. Diagramming a LAN with Routers • Notice in the graphic that the two networks are kept separate by the router. • Each switch serves a different network regardless of the physical location of the devices. • To create another physical network in a structured Layer 1 wiring scheme, simply patch the HCC and VCC into the correct switch.

29. Logical & Physical Network Maps • After determining your Layer 1, 2, and 3 design, you can create your addressing (logical) and physical maps. These are invaluable. They • Give a snapshot of the network • Show subnet mask info • Help in troubleshooting

30. Table of Contents End Slide Show