ccna3 m5 switches
TRANSCRIPT
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CCNA – Semester3
Module 5
Switches
Objectives
• Four major goals of LAN design
• Steps in systematic LAN design
• Three-layer design model
• List Cisco three-layer switches and their features
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LAN Design
LAN Design Goals
• Design goals in most network include:
– Functionality
– Scalability
– Adaptability
– Manageability
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LAN Design Goals: Functionality
• The network must work.
• It must allow users to meet their job
requirements.
• The network must provide user-to-user anduser-to-application connectivi ty with
reasonable speed and reliability.
LAN Design Goals: Scalability
• The network must be able to grow.
• The initial design should grow without any
major changes to the overall design.
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LAN Design Goals: Adaptabil ity
• The network must be designed with an eye
toward future technologies.
• It should include no element that would
limit implementation of new technologiesas they become available.
LAN Design Goals: Manageability
• The network should be designed to
facilitate network monitoring and
management to ensure ongoing stability of
operation.
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LAN design considerations
• To maximize available LAN bandwidth and
performance, the following LAN design
considerations must be addressed:
– The function and placement of servers – Collision detection issues
– Segmentation issues
– Broadcast domain issues
The function and placement of servers
• Servers provide network services such as: file sharing,printing, communication, and application services.
• Each server is dedicated to one function, such as e-mail or file sharing.
• Servers can be categorized into two distinct classes:
– Enterprise servers• Supports all the users on the network (such as e-mail or DNS).
• Should be placed in the main distribution facility (MDF).
– Workgroup servers
• Supports a specific set of users.
• Should be placed in the intermediate distribution facility (IDF)closest to the users accessing them.
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Server placement
Bandwidth Domain
• A bandwidth domain is associated with one port on a
bridge or switch.
• In the case of an Ethernet switch, a bandwidth domain
is also known as a collision domain.
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Systematic steps
1. Gathering the users' requirements and
expectations
2. Analyzing requirements
3. Designing the Layer 1, 2, and 3 LAN
structure (that is, topology)
4. Documenting the logical and physical
network implementation
Availability requirements
• Availability measures the usefulness of the
network. Factors that may affect availabil ity:
– Throughput
– Response time
– Access to resources
• Every customer may have a distinct
definition of availability.
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Analyzing requirements
• The next step in designing a network is to
analyze the requirements of the network
and its users.
• Network user needs constant change, thenecessity to increase network bandwidth
grows too.
Develop LAN topology
• LAN topology design can be broken into
the following three unique categories of
the OSI reference model:
– Network layer
– Data link layer
– Physical layer
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LAN topology
Documentation
• The final step in LAN design methodology is todocument the physical and logical topology of thenetwork.
• Important LAN design documentation includes thefollowing:
– OSI layer topology map – LAN logical map
– LAN physical map
– Cut sheets
– VLAN logical map
– Layer 3 logical map
– Addressing maps
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Layer1 design goals
• Choose cable type.
• Identify work area and HCC.
• Identify MDF, IDF, HCC, VCC and POP.
• Choose Ethernet or Fast Ethernet.• Documentation and physical diagrams.
Logical diagram
• The logical diagram is the basic road map of the LAN
including the following elements:
– Specify the locations and identification of the MDF and IDF wiring
closets.
– Document the type and quantity of cabling used to interconnect theIDFs with the MDF.
– Document how many spare cables are available for increasing the
bandwidth between the wiring closets.
– Provide detailed documentation of all cable runs, the identification
numbers, and the port the run is terminated on at the HCC or VCC.
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Typical MDF in star topology
MDF and IDF
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HCC and VCC
Example: Wiring closet location
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Example: Cable documentation
Common Layer 2 devices
• Layer 2 devices provide: flow control, errordetection, error correction, and congestionreduction in the network.
• Layer 2 devices determine the size of the
collision domains and broadcast domains.• The two most common Layer 2 devices are
bridges and LAN switches.
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Layer 2 switch
Using router
• Allows for segmentation of the LAN into
unique physical and logical networks.
• Allow for connectivity to wide-area
networks (WANs), such as the Internet.• Determines traffic flow between unique
physical network segments based on Layer
3 addressing.
• Stops broadcasts from reaching other LAN
segments.
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VLAN and broadcast domains
• By using VLANs, you can:
– limit broadcast traffic to within a VLAN and thus
create smaller broadcast domains.
– provide security by creating the VLAN groups
according to function.
VLAN communication
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VLAN implementation
Diagramming a LAN that uses routers
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Documentation: Logical network MAP
LAN Switches
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LAN design model
• Network designs tend to fol low one of two general
strategies: mesh or hierarchical.
• In a mesh structure, the network topology is flat, all
routers perform essentially the same functions.
• In a hierarchical structure the network is organized inlayers, each of which performs one or more specific
functions.
Hierarchical model
• The construction of a LAN that satisfies the
needs of both medium and large-sized
organizations is more likely to be successful if a
hierarchical design model is used.• The use of a hierarchical design model wil l
make it easier to make changes to the network
as the organization grows.
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Three layer design
• The hierarchical design model includes the
following three layers:
– The access layer provides users in workgroups access to
the network. – The distribution layer provides policy-based connectivity.
– The core layer provides optimal transport between sites.
The core layer is often referred to as the backbone.
Three layer design
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Access Layer Overview
• The access layer is the entry point for user
workstations and servers to the network.
• In a campus LAN the device used at the access
layer can be a switch or a hub.
• Access layer functions also include MAC layer
fil tering and microsegmentation, VLAN
membership.
Access Layer
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Common access layer switches
• Access layer switches
operate at Layer 2 and
should be low cost and
high port density.
• The following Cisco
switches are commonly
used at the access layer:
– Catalyst 1900 series
– Catalyst 2820 series
– Catalyst 2950 series
– Catalyst 4000 series
– Catalyst 5000 series
Distribution layer overview
• It helps to define and separate the core.
• Policies can be applied and access control lists canfilter packets.
• Isolates network problems to the workgroups in which
they occur. – Aggregation of the wiring closet connections
– Broadcast/multicast domain definition
– Virtual LAN (VLAN) routing
– Any media transitions that need to occur
– Security
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Distribution layer
Distribution layer switches
• The distribution layer
switch must have high
performance.
• Switches in this layer are
referred to as multilayerswitches.
• The following Cisco
switches are suitable for
the distribut ion layer:
– Catalyst 2926G
– Catalyst 5000 family
– Catalyst 6000 family
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Core layer overview
• The core layer is a high-speed switching backbone.
• If they do not have an associated router module, an
external router is used for the Layer 3 funct ion.
• Should not perform any packet manipulation (as ACL).• Provided with redundant alternate paths gives stability
to the network in the event of a single device failure.
• The core can be designed to use Layer 2 or Layer 3
switching. Asynchronous Transfer Mode (ATM) or
Ethernet switches can be used.
Core layer
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Core layer switches
• The following Cisco
switches are suitable for
the core layer:
– Catalyst 6500 series
– Catalyst 8500 series
– IGX 8400 series
– Lightstream 1010
Summary
• The four major goals of LAN design The steps in
systematic LAN design
• Design issues associated with Layers 1, 2, 3
• The three-layer design model
• The functions of each layer in the three-layer model
• Cisco access layer switches and their features
• Cisco distr ibution layer switches and their features
• Cisco core layer switches and their features
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CCNA3 – Module5