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Module 12: Network Troubleshooting - Coggle Diagram
Module 12: Network Troubleshooting
12.1 Network Documentation
Network documentation is the process of recording the details of network devices, connections, configurations, and topology. Helps administrators understand how the network is structured.
Key Components
Topology Diagrams: Show physical and logical connections between devices.
Device Information: Includes IP addresses, hostnames, and interface details.
Configuration Files: Store settings and parameters for routers, switches, and firewalls.
Inventory Lists: Contain hardware models, serial numbers, and software versions.
Benefits:
Faster issue resolution.
Reduced downtime.
Better planning for network expansion or changes.
Clear documentation for new team members or audits.
12.2 Troubleshooting Process
The troubleshooting process is a structured method for identifying and resolving network issues efficiently.
Main Steps:
Identify the Problem: Gather information and define the issue clearly.
Establish a Theory: Form a hypothesis about possible causes.
Test the Theory: Verify the hypothesis through observation or testing.
Establish a Plan of Action: Determine steps to fix the problem with minimal disruption.
Implement the Solution: Apply the corrective action.
Verify Full System Functionality: Confirm that the issue is resolved and network performance is normal.
Document the Findings: Record the issue, cause, and resolution for future reference.
12.3 Troubleshooting Tools
Troubleshooting tools help detect, analyze, and solve network connectivity and performance problems.
Software Tools
ping: Tests reachability of a host and measures round-trip time.
traceroute / tracert: Shows the path packets take to a destination and identifies delays.
ipconfig / ifconfig: Displays IP configuration details.
netstat: Lists active connections and listening ports.
nslookup / dig: Tests DNS name resolution.
telnet / ssh: Tests connectivity to remote devices and ports.
Hardware Tools:
Cable Tester: Checks cable continuity and wiring faults.
TDR (Time Domain Reflectometer): Detects cable breaks and shorts.
Multimeter: Measures voltage and continuity in electrical cables.
Loopback Plug: Verifies port functionality.
Network Monitoring Tools:
Wireshark: Captures and analyzes packets.
SNMP Managers: Monitor performance and device status.
Syslog Servers: Collect and store log messages from devices.
12.4 Symptoms and Causes Networks Problems
Common Symptoms:
Slow network performance.
Intermittent connectivity.
Complete loss of connectivity.
IP address conflicts.
DNS resolution failures.
High packet loss or jitter.
Possible Causes:
Physical Layer Issues: Damaged cables, loose connections, bad ports.
Configuration Errors: Wrong IP settings, VLAN mismatches, ACL misconfigurations.
Hardware Failures: Faulty switches, routers, or NICs.
Software Problems: Corrupt firmware, outdated drivers, or bugs.
Security Issues: Unauthorized access, malware, or denial-of-service attacks.
Congestion and Overutilization: Excessive bandwidth use or broadcast storms.
12.5 Troubleshooting IP Connectivity
Typical Issues:
Incorrect IP addressing or subnet mask.
Missing or wrong default gateway.
DNS misconfiguration.
Duplicate IP addresses.
Routing problems or missing routes.
Troubleshooting steps:
Check Physical Layer: Verify cables, interfaces, and link LEDs.
Test IP Configuration: Use ipconfig or ifconfig to confirm IP address, subnet, and gateway.
Ping Local Gateway: Confirms LAN connectivity.
Ping Remote Host: Tests routing beyond the local network.
Use traceroute: Identify where packets fail along the path.
Check DNS Resolution: Use nslookup to verify domain name resolution.
Review Routing Table: Use show ip route or route print to confirm valid routes.