Ca Ex S4 C8 Network Troubleshooting
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Transcript of Ca Ex S4 C8 Network Troubleshooting
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CCNA – Semester 4
Chapter 8: Network Troubleshooting
CCNA Exploration 4.0
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Objectives
• Establish and document a network baseline.
• Describe the various troubleshooting methodologies and
troubleshooting tools.
• Describe the common issues that occur during WAN
implementation.
• Identify and troubleshoot common enterprise network
implementation issues using a layered model approach.
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Establishing the
Network Performance Baseline
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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 for this
network should be under normal operating conditions. This
information is called the network baseline.
• Network documentation should include these components:
– Network configuration table
– End-system configuration table
– Network topology diagram
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Network configuration table
• Contains accurate, up-to-date records of the hardware and
software used in a network.
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End-system Configuration Table
• Contains baseline records of the hardware and software used in end-system devices such as servers, network management consoles, and desktop workstations.
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Network Topology Diagram
• Graphical representation of a network, which illustrates how
each device in a network is connected and its logical
architecture.
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Documenting Your Network
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Network Documentation Process
• When you document your network, you may have to gather
information directly from routers and switches. Commands
that are useful to the network documentation process
include:
– The ping command
– The telnet command
– The show ip interface brief command
– The show ip route command
– The show cdp neighbor detail command
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Documenting Your Network
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Why Is Establishing a Network Baseline
Important?
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Steps for Establishing a Network Baseline
• Planning for the First Basline
• Step 1. Determine what types of data to collect
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Steps for Establishing a Network Baseline
• Step 2. Identify devices and ports of interest
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Steps for Establishing a Network Baseline
• Step 3. Determine the baseline duration
It is important that the length of time and the baseline
information being gathered are sufficient to establish a
typical picture of the network.
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Steps for Establishing a Network Baseline
Measuring Network Performance Data
• Automated Data Collection: Fluke Network SuperAgent
module
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Steps for Establishing a Network Baseline
Measuring Network Performance Data
• Manual Commands
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Troubleshooting Methodologies and
Tools
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A General Approach to Troubleshooting
• Network engineers, administrators, and support personnel
realize that troubleshooting is a process that takes the
greatest percentage their time.
• Two extreme approaches to troubleshooting almost always
result in disappointment, delay, or failure.
– The theorist, or rocket scientist, approach
– The impractical, or caveman, approach.
• 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.
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A General Approach to Troubleshooting
• The caveman: first instinct is to start
swapping cards, cables, hardware, and
software until miraculously the network
begins operating again.
• Since both of these approaches are
extremes, the better approach is
somewhere in the middle using elements
of both. It is important to analyze the
network as a whole rather than in a
piecemeal fashion. A systematic
approach minimizes confusion and cuts
down on time otherwise wasted with trial
and error.
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Using Layered Models for Troubleshooting
• OSI Versus TCP/IP Layered Models
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General Troubleshooting Procedures
• General troubleshooting process:
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Troubleshooting Methods
• There are three main methods for troubleshooting networks:
– Bottom up
– Top down
– Divide and conquer
• Bottom-Up Troubleshooting Method
– Good approach to use when the
problem is suspected to be a
physical one.
– Disadvantage: requires checking
every device and interface
until the possible cause of the
problem is found.
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Troubleshooting Methods
• Top-Down Troubleshooting Method
– Use for simpler problems or when
you think the problem is with a piece
of software.
– Disadvantage: requires checking
every network application until the
possible cause of the problem is
found.
• Divide-and-Conquer Troubleshooting
Method
– You select a layer and test in both
directions from the starting layer.
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Troubleshooting Methods
• Guidelines for Selecting a Troubleshooting Method
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Gathering Symptoms
• Step 1. Analyze existing symptoms
• Step 2. Determine ownership
• Step 3. Narrow the scope
• Step 4. Gather symptoms from suspect devices
• Step 5. Document symptoms
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Gathering Symptoms
• Use the Cisco IOS commands to gather symptoms about the
network.
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Gathering Symptoms
• Questioning End Users
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Software Troubleshooting Tools
• NMS Tools
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Software Troubleshooting Tools
• Knowledge Bases
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Software Troubleshooting Tools
• Baselining Tools
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Software Troubleshooting Tools
• Protocol Analyzers
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Hardware Troubleshooting Tools
• Network Analysis Module (NAM)
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Hardware Troubleshooting Tools
Digital Multimeters Cable Testers
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Hardware Troubleshooting Tools
Cable Analyzers Portable Network Analyzers
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Research Activity
• Software Tools– Network Management Systems:
• http://www.ipswitch.com/products/whatsup/index.asp?t=demo
• http://www.solarwinds.com/products/network_tools.aspx
• http://h20229.www2.hp.com/products/cvnnm/ds/cvnnm_ds.pdf
– Baselining Tools:
• http://www.networkuptime.com/tools/enterprise/
• http://www.neon.com/Tutorials/index.html?drawyournetworkmap.htm
– Knowledge Bases:
• http://www.cisco.com
– Protocol Analyzers:
• http://www.flukenetworks.com/fnet/en-us/products/OptiView+Protocol+Expert/
• Hardware Tools– Cisco Network Analyzer Module (NAM):
• http://www.cisco.com/en/US/docs/net_mgmt/network_analysis_module_software/3.5/user/guide/user.html
– Cable Testers:
• http://www.flukenetworks.com/fnet/en-us/products/CableIQ+Qualification+Tester/Demo.htm
– Cable Analyzers:
• http://www.flukenetworks.com/fnet/en-us/products/DTX+CableAnalyzer+Series/Demo.htm
– Network Analyzers:
• http://www.flukenetworks.com/fnet/en-us/products/OptiView+Series+III+Integrated+Network+Analyzer/Demos.htm
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Common WAN Implementation Issues
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WAN Communications
• A communications provider
owns the data links that make
up a WAN.
• Speed (BW) is considerably
slower than LAN bandwidth.
• WANs carry a variety of traffic types, such as data, voice,
and video.
• Older WANs often consisted of data links directly connecting
remote mainframe computers.
• Today's WANs connect geographically separated LANs.
WAN technologies function at the lower three layers of the
OSI reference model
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Steps in WAN Design
LOCATE LANs
ANALYZE TRAFFICS
PLAN TOPOLOGY
PLAN BANDWIDTH
CHOOSE
TECHNOLOGY
COST AND EVALUATE
IterateReview
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WAN Traffic Considerations
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WAN Topology Considerations
Star or Hub-and-SpokeFull-Mesh
Partial-Mesh
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WAN Connection Technologies
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WAN Topology Considerations
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WAN Bandwidth Considerations
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Common WAN Implement Issues
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Case Study: WAN Troubleshooting from a
ISP’s Perspective
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Network Troubleshooting
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Interpreting Network Diagrams to Identify
Problems
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Interpreting Network Diagrams to Identify
Problems
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Physical Layer Troubleshooting
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Physical Layer Troubleshooting
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Physical Layer Troubleshooting
• Troubleshooting
Layer 1 Problems
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Data Link Layer Troubleshooting
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Data Link Layer Troubleshooting
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Troubleshooting Layer 2 - PPP
• Step 1: Check that the appropriate encapsulation is in use at
both ends
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Troubleshooting Layer 2 - PPP
• Step 2: Confirm that the Link Control Protocol (LCP)
negotiations have succeeded
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Troubleshooting Layer 2 - PPP
• Step 3: Verify authentication on both sides of the link
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Troubleshooting Layer 2 – Frame Relay
• Step 1: Verify the physical connection between the
CSU/DSU and the router.
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Troubleshooting Layer 2 – Frame Relay
• Step 2: Verify proper LMI information exchange between
each router and the FR switch.
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Troubleshooting Layer 2 – Frame Relay
• Step 3: Verify that PVC status is active
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Troubleshooting Layer 2 – Frame Relay
• Step 4: Verify that Frame Relay encapsulation matches on
both routers
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Troubleshooting Layer 2 - STP Loops
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Network Layer Troubleshooting
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Network Layer Troubleshooting
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Transport Layer Troubleshooting
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Transport Layer Troubleshooting
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Transport Layer Troubleshooting
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Application Layer Troubleshooting
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Application Layer Troubleshooting
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Application Layer Troubleshooting
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Application Layer Troubleshooting
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Application Layer Troubleshooting
Activity: 8.4.6.5
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Summary
In this chapter, you have learned to:
• Establish and document a network baseline.
• Describe the various troubleshooting methodologies and
troubleshooting tools.
• Describe the common issues that occur during WAN
implementation.
• Identify and troubleshoot common enterprise network
implementation issues using a layered model approach.