1 13-jun-15 s ward abingdon and witney college lan design ccna exploration semester 3 chapter 1
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18 Apr 2023 S Ward Abingdon and Witney College 1
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
LAN Design
Basic Switch Concepts
VLANs
VTP
STP
Inter-VLAN routing
Wireless
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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?
Document it now
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Choosing switches (contd)
Form factor Fixed configuration
– ports on chassis Modular – ports on
cards Stackable – act as
one switch, linked by special ports.
1 rack unit (1U)
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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
Concentrate on general
features
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The End