LAN design
CCNA Exploration Semester 3
Chapter 1
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Topics
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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
Wireless
VLANs
STP
VTP
Inter-VLAN
routing
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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
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Small network: merged core and distribution
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Logical and physical layout
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Logical – how
they connect.
Physical – where
they are.
Logical
connections not
obvious from
looking.
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Benefits of Hierarchical Network
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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
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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
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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
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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
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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?
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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.
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1 rack unit (1U)
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Choosing switches (contd)
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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)
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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
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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
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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
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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
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