Chapter 5 - section 5.5 - Given a scenario, use the appropriate tool or protocol to solve networking issues.

section 5.5

Objective – Network Troubleshooting Tools and Commands

• Software tools
▸ Protocol analyzer
▸ Command line tools
▸ ping
▸ traceroute / tracert
▸ nslookup
▸ tcpdump
▸ dig
▸ netstat
▸ ip / ifconfig / ipconfig
▸ arp
▸ Nmap
▸ LLDP / CDP
▸ Speed tester
• Hardware tools
▸ Toner
▸ Cable tester
▸ Taps
▸ Wi-Fi analyzer
▸ Visual fault locator
• Basic networking device commands
▸ show mac-address-table
▸ show route
▸ show interface
▸ show config
▸ show arp
▸ show vlan
▸ show power

Software Tool – Protocol Analyzer

• Captures and analyzes network traffic
• Example: Wireshark
• Used to inspect packets and protocols
• Essential for troubleshooting (exam)

Command Line Tool – ping

• Tests basic network connectivity
• Uses ICMP echo requests
• Measures latency and packet loss
• First troubleshooting step (exam)

Command Line Tool – traceroute / tracert

• Shows path packets take to destination
• Identifies where delays or failures occur
• traceroute (Linux/macOS), tracert (Windows)
• Uses TTL values

Command Line Tool – nslookup

• Queries DNS servers
• Verifies name resolution
• Helps diagnose DNS issues
• Common exam utility

Command Line Tool – tcpdump

• Command-line packet capture tool
• Used on Linux systems
• Filters traffic in real time
• Lightweight protocol analyzer

Command Line Tool – dig

• DNS lookup and diagnostic tool
• Provides detailed DNS responses
• Preferred over nslookup on Linux
• Useful for DNSSEC validation

Command Line Tool – netstat

• Displays active connections
• Shows listening ports and routing table
• Used to identify open services
• Security and troubleshooting tool

Command Line Tool – ip / ifconfig / ipconfig

• Displays and configures IP settings
• ip (modern Linux)
• ifconfig (legacy Unix/Linux)
• ipconfig (Windows)
• Exam expects OS differences

Command Line Tool – arp

• Displays ARP cache
• Maps IP addresses to MAC addresses
• Used to detect ARP issues
• Helpful for duplicate IP troubleshooting

Software Tool – Nmap

• Network scanning and discovery tool
• Identifies hosts and open ports
• Used for security and troubleshooting
• Commonly referenced in exams

Discovery Protocol – LLDP / CDP

• LLDP: vendor-neutral discovery protocol
• CDP: Cisco proprietary
• Identifies neighboring devices
• Helps map network topology

Software Tool – Speed Tester

• Measures bandwidth and throughput
• Identifies performance issues
• Internet and LAN testing
• Confirms ISP link speed

Hardware Tool – Toner

• Traces cable paths
• Used to identify cable endpoints
• Common in wiring closets
• Physical layer tool

Hardware Tool – Cable Tester

• Tests cable continuity and wiring
• Detects shorts, opens, and miswires
• Essential for physical troubleshooting
• Exam-relevant hardware tool

Hardware Tool – Taps

• Copies network traffic for monitoring
• Passive or active
• Used with protocol analyzers
• Does not interrupt traffic

Hardware Tool – Wi-Fi Analyzer

• Measures wireless signal strength
• Identifies interference and channel overlap
• Used for wireless optimization
• Common troubleshooting tool

Hardware Tool – Visual Fault Locator

• Uses visible laser light
• Identifies fiber breaks or bends
• Short-distance fiber troubleshooting
• Physical fiber diagnostics

Device Command – show mac-address-table

• Displays MAC address table
• Shows learned MACs per port
• Used for switching issues
• Layer 2 troubleshooting

Device Command – show route

• Displays routing table
• Shows learned and static routes
• Used for routing verification
• Exam expects route interpretation

Device Command – show interface

• Displays interface status and counters
• Shows errors and bandwidth usage
• Used for physical and data-link issues
• Key troubleshooting command

Device Command – show config

• Displays device configuration
• Used to verify settings
• Important for change validation
• Security and troubleshooting use

Device Command – show arp

• Displays ARP table
• Maps IPs to MAC addresses
• Detects ARP issues
• Useful for duplicate IP detection

Device Command – show vlan

• Displays VLAN configuration
• Shows VLAN membership
• Used for VLAN troubleshooting
• Layer 2 verification

Device Command – show power

• Displays PoE status
• Shows power usage per port
• Used to troubleshoot PoE issues
• Exam-relevant command

N10-009 Sample Questions – Tools and Commands

• Q: Which tool captures packets for analysis?
▸ A: Protocol analyzer
• Q: Which command tests basic connectivity?
▸ A: ping
• Q: Which tool identifies wireless interference?
▸ A: Wi-Fi analyzer
• Q: Which command shows learned MAC addresses?
▸ A: show mac-address-table