Linux Networking Commands

Linux provides powerful tools for monitoring, diagnosing, and troubleshooting network issues. Below, we explore essential commands and how to use them effectively.

Checking Connectivity

pingtraceroute

• Usage: Test connectivity to a host.

  ping google.com
  

• Sends ICMP packets to the destination and measures the response time.

• Use Ctrl+C to stop the command.

• Troubleshooting Example:

  • If ping fails, it could indicate:
  • Network connectivity issues.
  • DNS resolution problems.

• Usage: Trace the path packets take to a destination.

  traceroute google.com
  

• Identifies where delays or failures occur in the route.

• Troubleshooting Example:

  • Use traceroute to pinpoint where packets are getting dropped.

Viewing Network Configuration

ip addrifconfig (Deprecated)

• Usage: Display network interfaces and IP addresses.

  ip addr
  

• Look for inet to find assigned IPs.

• Troubleshooting Example:

  • If no IP is assigned, check your DHCP configuration or static IP settings.

• Usage: Similar to ip addr but older.

  ifconfig
  

Examining Network Connections

netstatss

• Usage: Display network connections, routing tables, and more.

  netstat -an
  

• Usage: Faster, modern replacement for netstat.

  ss -tuln
  

  -Troubleshooting Example:
  • Use ss to identify open ports and active connections.

Querying DNS

nslookupdig

• Usage: Query DNS for IP addresses.

  nslookup google.com
  

• Usage: Advanced DNS query tool.

  dig google.com
  

• Troubleshooting Example:
  • Use nslookup or dig to verify DNS resolution.
  • If DNS fails, check your /etc/resolv.conf file or DNS server configuration.