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MODULE 12: NETWORK TROUBLESHOOTING - Coggle Diagram
MODULE 12: NETWORK TROUBLESHOOTING
12.1 Network Documentation
12.1.4 Establish a Network Baseline
12.1.5 Step 1 - Determine What Types of Data to Collect
When conducting the initial baseline, start by selecting a few variables that represent the defined policies. If too many data points are selected, the amount of data can be overwhelming, making analysis of the collected data difficult. Start out simply and fine-tune along the way. Some good starting variables are interface utilization and CPU utilization.
12.1.3 Network Device Documentation
LAN Switch Device Documentation
End-system Documentation Files
Router Device Documentation
12.1.6 Step 2 - Identify Devices and Ports of Interest
12.1.2 Network Topology Diagrams
Logical IPv4 Topology
Logical IPv6 Topology
Physical Topology
12.1.7 Step 3 - Determine the Baseline Duration
12.1.1 Documentation Overview
12.1.8 Data Measurement
12.5 Troubleshooting IP Connectivity
12.5.6 Troubleshoot VLAN Assignment Example
Assume for example, that in an effort to improve the wire management in the wiring closet, your company has reorganized the cables connecting to switch S1.
12.5.7 Step 4 - Verify Default Gateway
12.5.5 Step 3 - Verify Addressing on the Local Network
The arp Windows command displays and modifies entries in the ARP cache that are used to store IPv4 addresses and their resolved Ethernet physical (MAC) addresses. As shown in the command output, the arp Windows command lists all devices that are currently in the ARP cache.
12.5.9 Step 5 - Verify Correct Path
12.5.4 Step 2 - Check for Duplex Mismatches
12.5.11 Step 7 - Verify ACLs
12.5.3 Step 1 - Verify the Physical Layer
12.5.8 Troubleshoot IPv6 Default Gateway Example
In IPv6, the default gateway can be configured manually, using stateless autoconfiguration (SLAAC), or by using DHCPv6. With SLAAC, the default gateway is advertised by the router to hosts using ICMPv6 Router Advertisement (RA) messages.
12.5.2 End-to-End Connectivity Problem Initiates Troubleshooting
12.5.10 Step 6 - Verify the Transport Layer
12.5.1 Components of Troubleshooting End-to-End Connectivity
12.5.12 Step 8 - Verify DNS
The DNS protocol controls the DNS, a distributed database with which you can map hostnames to IP addresses. When you configure DNS on the device, you can substitute the hostname for the IP address with all IP commands, such as ping or telnet.
12.3 Troubleshooting Tools
12.3.2 Protocol Analyzers
12.3.3 Hardware Troubleshooting Tools
12.3.1 Software Troubleshooting Tools
Baselining Tools
Many tools for automating the network documentation and baselining process are available. Baselining tools help with common documentation tasks. For example, they can draw network diagrams, help keep network software and hardware documentation up-to-date.
Knowledge Bases
Online network device vendor knowledge bases have become indispensable sources of information. When vendor-based knowledge bases are combined with internet search engines, a network administrator has access to a vast pool of experience-based information.
Network Management System Tools
Network management system (NMS) tools include device-level monitoring, configuration, and fault-management tools. These tools can be used to investigate and correct network problems. Network monitoring software graphically displays a physical view of network devices, allowing network managers to monitor remote devices continuously and automatically.
12.3.4 Syslog Server as a Troubleshooting Tool
12.2 Troubleshooting Process
12.2.1 General Troubleshooting Procedures
12.2.2 Seven-Step Troubleshooting Process
12.2.3 Question End Users
12.2.4 Gather Information
12.2.5 Troubleshooting with Layered Models
12.2.6 Structured Troubleshooting Methods
Bottom-Up
Top-Down
Divide-and-Conquer
Follow-the-Path
This is one of the most basic troubleshooting techniques. The approach first discovers the traffic path all the way from source to destination.
Substitution
This approach is also called swap-the-component because you physically swap the problematic device with a known, working one. If the problem is fixed, then the problem is with the removed device. If the problem remains, then the cause may be elsewhere.
Comparison
This approach is also called the spot-the-differences approach and attempts to resolve the problem by changing the nonoperational elements to be consistent with the working ones. You compare configurations, software versions, hardware, or other device properties, links, or processes between working and nonworking situations and spot significant differences between them.
Educated Guess
This approach is also called the shoot-from-the-hip troubleshooting approach. This is a less-structured troubleshooting method that uses an educated guess based on the symptoms of the problem. Success of this method varies based on your troubleshooting experience and ability.
12.2.7 Guidelines for Selecting a Troubleshooting Metho
12.4 Symptoms and Causes of Network Problems
12.4.1 Physical Layer Troubleshooting
12.4.2 Data Link Layer Troubleshooting
12.4.3 Network Layer Troubleshooting
12.4.4 Transport Layer Troubleshooting - ACLs
12.4.5 Transport Layer Troubleshooting - NAT for IPv4
12.4.6 Application Layer Troubleshooting
