Network Troubleshooting Commands

Importance of Understanding Device Configuration

• Essential to know IP addresses, subnet masks, DNS settings, and other IP configurations.
• ipconfig command in Windows provides detailed network configuration.
  • Displays adapter information, IP details (IPv4 and IPv6).
  • Shows hostname, IP address, subnet mask, default gateway.
  • Use ipconfig /all for more detailed information, including DHCP and DNS server details.

Ping Command

• Used to check communication with another device on the network.
• Sends requests and measures round-trip time.
• Example: Ping to the Quad 9 server (9.9.9.9).
  • Sends four requests, measures response time, TTL (Time to Live).
  • Useful for initial network communication checks.

Netstat Command

• Stands for network statistics, available on Windows, Linux, macOS.
• Displays active connections and listening ports.
  • netstat -a: Shows all connections and listening ports.
  • netstat -b: Shows binaries, requires admin privileges.
  • netstat -n: Shows IP addresses only, without name resolution.
• Use elevated command prompt for certain options (e.g., netstat -b).

NSLookup Command

• Resolves domain names to IP addresses.
• Example: nslookup www.professormesser.com.
  • Queries DNS server to find the IP address for a domain.
  • Can show multiple IP addresses for redundancy.

Windows NET Command

• Summarizes Windows-specific commands related to networking.
  • net view: Shows available shares on a remote server.
  • net use: Maps a drive to a network share.
  • net user: Views and manages user accounts.

Traceroute Command

• Identifies the route packets take to reach a destination.
• Windows command: tracert.
  • Uses ICMP protocol and TTL (Time to Live) to trace routes.
  • Displays each hop along the path to the destination.
• Useful for diagnosing routing problems or examining the network path.

Pathping Command

• Combines features of Ping and Traceroute.
• Measures round-trip time and packet loss for each hop.
• Takes longer but provides detailed insights into network issues.
• Example command: pathping -n 9.9.9.9 displays only IP addresses.

Summary

• These commands are essential for diagnosing and understanding network issues.
• Knowing when and how to use each command can help quickly identify and resolve connectivity problems.