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Copyright 2002 Year 2 - Chapter 4/Cisco 3 - Module 4 LAN Design By Carl Marandola
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Copyright 2002
Year 2 - Chapter 4/Cisco 3 - Module 4
LAN Design
By
Carl Marandola
Copyright 2002
Objectives• Explain LAN design goals
• Identify LAN design issues
• Explain network design methodology
• Describe how to gather and analyze network equipment
• Identify Layer 1 (media and topology) design issues
• Identify Layer 2 (LAN switching) design issues
• Identify Layer 3 (routing) design issues
• Describe the physical and logical network implementation documentation
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LAN Design Goals • Functionality
– The network must work.
• Scalability– The network must be able to grow and contract to
meet the needs of the organization.
• Adaptability– The network must adapt to new technologies.
• Manageability– The network must support network monitoring and
management.
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Critical Components of LAN Design
• Function and Placement of Servers• Intranets• Collision Detection (Ethernet)• Segmentation• Bandwidth Versus Broadcast Domains
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Server Placement
• Servers can be categorized into two distinct classes:– Enterprise servers
– Workgroup (departmental) servers
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Intranets
• Centralized Web Servers (Comparable to Enterprise Servers)
• Limited to Internal Users– Those that have logged in to corporate network
• Accessed by Web Browser• Many Day-to-Day Job Functions on the Web
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Collision Detection (Ethernet)
• Legacy Ethernet– Contention refers to excessive collisions caused
by too many devices vying for services.– Broadcasts becomes excessive when:
• Too many client packets looking for services• Too many server packets announcing services• Too many routing table updates• Too many broadcast-dependent protocols, such as ARP,
DHCP, and so forth
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Broadcast and Collision Domains
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Network Design Methodology
• Gathering Requirements• Analyzing Requirements• Designing the Network Topology
– Designing the Layer 1, 2, and 3 LAN structure– Documenting the logical and physical network
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Gathering Requirements• Who will be using the network?
– What resources do they need to access?– What is their level of skill?– What are their attitudes toward computers and
applications?
• What data and processes are mission-critical?• What protocols are allowed on the network?• What desktop hosts (OSs) are supported?• Who has authority over addressing, naming,
topology design, and configuration?• What about the existing computer hardware and
software?– How are these resources currently linked and shared?
• What financial resources are available?– Who controls these resources?
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Analyzing Requirements
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Develop a Physical Topology
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OSI Layer 1, 2, and 3 Issues
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Layer 1 Topology: Signaling Method, Medium Type, and Maximum Length
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MDF in a Star Topology
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MDFs and IDFs
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Extended Star
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10BaseT, 100BaseTX, and 1000BaseX Ethernet
• 10 Mbps (and 100 Mbps) to desktops
• Vertical cabling 100 Mbps (or Gigabit) between MDFs and IDFs
• 100 Mbps (or Gigabit) server to network
• Often multiple links combined into channels to provide increased bandwidth in vertical runs and server connections
Fast Ethernet or Gigabit Ethernet
Fast Ethernet or Gigabit Ethernet
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Elements of a Logical Topology Diagram
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Cut Sheet
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Select Layer 2 Devices
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Asymmetric Switching
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Switches to Reduce Congestion
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Determining the Number of Cable Runs and Drops
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Hubs Share (Split) Bandwidth
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Switches, Hubs, and Collision Domains
Switches combined with full-duplex create collision-free domains.
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Layer 3 Design
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VLANs in the Design
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Routers Provides Logical Structure to a Network
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Diagramming a Standards-Based LAN with Routers
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Logical Maps
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Addressing Maps
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Physical Maps
