LAN design

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LAN design

• CCNA Exploration Semester 3
• Chapter 1

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Topics

• Networks and business needs
• The 3-level hierarchical network design model
• Including voice and video over IP in the design
• Devices at each layer of the hierarchy
• Cisco switches for each layer

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Semester 3
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Hierarchical design model
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Hierarchical design model
High speed backbone.
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Hierarchical design model
Subnets, VLANs, routing, flow control, security.
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Hierarchical design model
Connects end devices. Controls which devices
connect.
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Collapsed core

• Small network merged core and distribution

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Logical and physical layout

• Logical how they connect.
• Physical where they are.
• Logical connections not obvious from looking.

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Benefits of Hierarchical Network

• Scalability easy to expand
• Redundancy at core and distribution layers
• Performance route packets through fast devices
• Security at access and distribution layers
• Manageability similar functions within layer
• Maintainability - modular

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Design principles

• Network diameter how many devices must packet
  pass through? Keep it low.
• Bandwidth aggregation combine ports where high
  bandwidth is needed.
• Redundant links/devices in core and
  distribution layers. Too expensive for access.
• Start design at the access layer. How many
  devices, how much bandwidth needed?

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Converged network

• Combines data, voice, video.
• (Not converged as in all routers have consistent
  information. Same word used.)
• Needs quality of service (QoS) to give priority
  to voice and video.
• Was very expensive, needed expertise, needed to
  replace legacy equipment.
• Now more affordable.

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Advantages of converged network

• One network to manage/ keep up to date
• One set of cabling and networking devices
• One group of people to run it
• One service provider
• Can have voice and video on PC using headset,
  webcam and software no separate equipment.

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Choosing switches

• Carry out Traffic Flow Analysis using software to
  monitor amount and source of traffic. Allow for
  growth.
• Carry out User Communities Analysis. Group by job
  function. How many ports? How much bandwidth?
  Allow for growth.
• Carry out Data Stores and Data Servers analysis.
  Traffic to, from, between.

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Topology Diagram
Ports?Bandwidth?Bottlenecks?
Layers?Routes?Redundancy?
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Topology Diagram
Ports?Bandwidth?Bottlenecks?
Layers?Routes?Redundancy?
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Choosing switches (contd)
1 rack unit (1U)

• Form factor
• Fixed configuration ports on chassis
• Modular ports on cards
• Stackable act as one switch, linked by special
  ports.

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Choosing switches (contd)

• Port density how many ports? (Allow for links
  between switches.)
• Forwarding rate How many Gbps can it process?
  Can all ports work simultaneously at maximum
  speed?
• Link aggregation (EtherChannel) up to 8 ports
  bound together, acting as one, with combined
  bandwidth can it do this?

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Choosing switches (contd)

• Power over Ethernet (PoE) for IP phones, network
  access points. Do you need it? It adds to the
  cost.
• Multilayer switch needed? Typical switch works at
  Data Link layer (2), uses MAC addresses.
  Multilayer also works at Network layer (3),
  routes between subnets.

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Access Layer Switch Features

• Port security choose which devices may connect.
  All Cisco switches support this.
• VLANs connected devices on different subnets.
• Speed Fast Ethernet (100Mbps) or Gigabit.
• Power over Ethernet (PoE) expensive
• Link aggregation for uplinks
• Quality of service (QoS) if needed

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Distribution Layer Switch Features

• Layer 3 support route between VLANs
• High forwarding rate (processing)
• Port speed Gbps, 10Gbps ports
• Redundancy
• Security Access control lists
• Link aggregation
• Quality of service
• Availability. Hot swappable power supply?

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Core Layer Switch Features

• Support for Network layer (3) - routing
• Very high forwarding rate
• Very high port speed (1Gbps, 10Gbps)
• Redundancy
• Link aggregation
• Quality of service
• Avoid security and other distractions here. Go
  for speed.

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Catalyst Switch product lines
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Catalyst Switch product lines
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• The End