CCNA
Cisco Certified Network Associate
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Documenting your network
 To efficiently diagnose and correct network
problems, a network engineer needs to know how a
network has been designed and what the expected
performance.
 Network documentation should include these
components:
 Network configuration table
 End-system configuration table
 Network topology diagram
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Documenting your network
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Documenting your network
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Documenting your network
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Documenting your network
 Commands that are useful to the network
documentation process include:
 Ping
 telnet
 Show ip interface brief
 Show ip route
 Show cdp neighbor detail
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Establishing the network
performance baseline
 This information helps to determine the "personality" of the
network and provides answers to the following questions:
 How does the network perform during a normal or average
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day?
Where are the underutilized and over-utilized areas?
Where are the most errors occurring?
What thresholds should be set for the devices that need to be
monitored?
Can the network deliver the identified policies?
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Steps for establishing a network
baseline
 Determine what types of data to collect
 some good starting measures are interface utilization and CPU utilization.
 Identify devices and ports of interest
 Network device ports that connect to other network devices
 Servers
 Key users
 Anything else considered critical to operations
 Determine the baseline duration
 t is important that the length of time and the baseline information being gathered are
sufficient to establish a typical picture of the network. This period should be at least
seven days to capture any daily or weekly trends. Weekly trends are just as important as
daily or hourly trends.
 A baseline needs to last no more than six weeks, unless specific long-term trends need
to be measured. Generally, a two-to-four-week baseline is adequate.
 You would get an inaccurate measure of network performance if you performed a
baseline measurement on a holiday or during a month when most of the company is on
vacation.
 Analysis must be conducted regularly to understand how the network is affected by
growth and other changes.
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Steps for establishing a network
baseline
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Steps for establishing a network
baseline
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Steps for establishing a network
baseline
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Steps for establishing a network
baseline
 Sophisticated network management software is often used to
baseline large and complex networks. For example, the Fluke
Network SuperAgent module enables administrators to
automatically create and review reports using its Intelligent
Baselines feature.
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Methodologies and tools
 The rocket scientist analyzes and reanalyzes the situation until the
exact cause at the root of the problem has been identified and
corrected with surgical precision.
 The caveman's first instinct is to start swapping cards, cables,
hardware, and software until miraculously the network begins
operating again.
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Using Layered Models
 if the symptoms suggest a physical connection problem, the
network technician can focus on troubleshooting the circuit that
operates at the Physical layer. If that circuit functions properly, the
technician looks at areas in another layer that could be causing the
problem.
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General Procedures
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Methods
 There are three main methods for troubleshooting networks:
 Bottom up
 Top down
 Divide and conquer
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Methods - Bottom up
 good approach to use when the problem is suspected to be a
physical one. Most networking problems reside at the lower levels,
so implementing the bottom-up approach often results in effective
results.
 it requires that you check every device and interface on the
network until the possible cause of the problem is found.
Remember that each conclusion and possibility must be
documented so there can be a lot of paper work associated with
this approach. A further challenge is to determine which devices to
start examining first.
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Methods – Top Down
 Use this approach for simpler problems or when you think the
problem is with a piece of software.
 The disadvantage with the top-down approach is it requires
checking every network application until the possible cause of the
problem is found.
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Methods – Divide and conquer
 start by collecting user experience of the problem, document the
symptoms and then, using that information, make an informed
guess as to which OSI layer to start your investigation. Once you
verify that a layer is functioning properly, assume that the layers
below it are functioning and work up the OSI layers. If an OSI layer
is not functioning properly, work your way down the OSI layer
model.
 For example, if users can't access the web server and you can ping
the server, then you know that the problem is above Layer 3. If you
can't ping the server, then you know the problem is likely at a lower
OSI layer.
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Ghetering symptoms
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Ghetering symptoms
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Software Tools
 A wide variety of software and hardware tools are
available to make troubleshooting easier. These tools
may be used to gather and analyze symptoms of
network problems and often provide monitoring and
reporting functions that can be used to establish the
network baseline.
 NMS tools
 Knowledge bases
 Baselining tools
 Protocol analyzer
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Software Tools – NMS Tools
 Network management system (NMS) tools include
device-level monitoring, configuration, and fault
management tools.
 Examples of commonly used network management
tools are CiscoView, HP Openview, Solar Winds, and
What's Up Gold.
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Software Tools – Knowledge bases
 The figure shows the Cisco Tools & Resources page
found at http://www.cisco.com. This is a free tool
providing information on Cisco-related hardware and
software. It contains troubleshooting procedures,
implementation guides, and original white papers on
most aspects of networking technology.
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Software Tools – Baselining tools
 Many tools for automating the network documentation
and baselining process are available.
 They can help you draw network diagrams, help you to
keep network software and hardware documentation
up-to-date and help you to cost-effectively measure
baseline network bandwidth use.
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Software Tools – Protocol analyzer
 A protocol analyzer decodes the various protocol layers
in a recorded frame and presents this information in a
relatively easy to use format.
 Most protocol analyzers can filter traffic that meets
certain criteria so that, for example, all traffic to and
from a particular device can be captured.
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Hardware Tools
 Network Analysis Module
 Digital Multimeters
 Cable Testers
 Cable Analyzers
 Portable Network Analyzers
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Hardware Tools - Network Analysis
Module
 A network analysis module (NAM) can be installed in Cisco
Catalyst 6500 series switches and Cisco 7600 series routers to
provide a graphical representation of traffic from local and
remote switches and routers.
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Hardware Tools - Digital Multimeters
 Instruments that are used to directly measure electrical
values of voltage, current, and resistance.
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Hardware Tools - Cable Testers
 Cabling testers can be used to detect broken wires, crossed-
over wiring, shorted connections, and improperly paired
connections. These devices can be inexpensive continuity
testers, moderately priced data cabling testers, or expensive
time-domain reflectometers (TDRs).
 TDRs are used to pinpoint the distance to a break in a cable.
These devices send signals along the cable and wait for them
to be reflected.
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Hardware Tools - Cable Analyzers
 Cable analyzers are multifunctional handheld devices that
are used to test and certify copper and fiber cables for
different services and standards. The more sophisticated
tools include advanced troubleshooting diagnostics that
measure distance to performance defect (NEXT, RL), identify
corrective actions, and graphically display crosstalk and
impedance behavior.
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Hardware Tools - Portable Network
Analyzers
 Portable devices that are used for troubleshooting switched
networks and VLANs. By plugging the network analyzer in
anywhere on the network, a network engineer can see the
switch port to which the device is connected and the average
and peak utilization. The analyzer can also be used to
discover VLAN configuration, identify top network talkers,
analyze network traffic, and view interface details.
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Wan Comunications
 WAN data transfer speed (bandwidth) is considerably slower
than the common LAN bandwidth.
 WANs carry a variety of traffic types, such as data, voice, and
video.
 The design selected must provide adequate capacity and
transit times to meet the requirements of the enterprise.
 topology of the connections between the various sites, the
nature of those connections, and bandwidth capacity.
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Wan Comunications – Steps in Design
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Wan Comunications – Steps in Design
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Wan Topologies
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Wan Topologies
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Wan Topologies
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Wan Topologies
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Wan Technologies
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Wan Technologies
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Interpreting network diagrams –
Physical network diagram
 Device type
 Model and manufacturer
 Operating system version
 Cable type and identifier
 Cable specification
 Connector type
 Cabling endpoints
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Interpreting network diagrams –
Physical network diagram
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Interpreting network diagrams –
Logical network diagram
 Device identifiers
 IP address and subnet
 Interface identifiers
 Connection type
 DLCI for virtual circuits
 Site-to-site VPNs
 Routing protocols
 Static routes
 Data-link protocols
 WAN technologies used
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Interpreting network diagrams –
Logical network diagram
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Physical Layer
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Physical Layer
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Data Link Layer
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Data Link Layer
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Data Link Layer
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Data Link Layer
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Data Link Layer
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Network Layer
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Network Layer
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Transport Layer
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Transport Layer
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Transport Layer
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Application Layer
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Application Layer
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Application Layer
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Application Layer
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