Skip to main content

Netstat

netstat (network statistics) is a versatile command-line tool that is invaluable for network administrators and engineers. It provides information about network connections, routing tables, interface statistics, masquerade connections, and multicast memberships.

Core Functionality of Netstat​

  1. Display Network Connections: netstat can list all incoming and outgoing network connections, including TCP and UDP ports on which the computer is listening and established connections.

  2. Routing Table Information: It displays the routing table of the host, including network destinations, gateways, and the number of hops to each destination.

  3. Interface Statistics: netstat shows network interface statistics, such as the number of packets sent and received, packet errors, and much more.

  4. Display Listening Ports: It can show all network ports on which the system is listening, which is crucial for troubleshooting and security audits.

  5. Display PID and Program Names: With certain options, netstat can display the process ID (PID) and the name of the program to which each socket belongs.

Use Cases of Netstat​

  1. Troubleshooting Network Issues: By showing active connections and listening ports, netstat helps identify if certain services are running or if unexpected services are listening, which could indicate a security breach.

  2. Monitoring Network Performance: Regular checks with netstat can help monitor the health and performance of network interfaces.

  3. Checking for Unauthorized Connections: It's a fundamental tool for security, used to check for unauthorized or unexpected connections, which could be indicative of malware or a hacker.

  4. Verifying Network Configuration: It helps in verifying if network routes are set up correctly.

Common Commands and Options​

  • netstat -a: Shows all active listening and non-listening sockets.
  • netstat -t: Displays TCP connections.
  • netstat -u: Displays UDP connections.
  • netstat -n: Shows addresses and port numbers in numerical form.
  • netstat -r: Shows the kernel routing table.
  • netstat -i: Displays a table of all network interfaces.
  • netstat -s: Shows network statistics grouped by protocol (like TCP, UDP, ICMP).
  • netstat -p: Shows the PID and the name of the program to which each socket belongs (useful for identifying which processes are using which ports).

Platform Variations​

  • While netstat is available on both Windows and Unix-like systems (Linux, macOS), some options and the output format can vary between these platforms.

Conclusion​

netstat is an essential tool for any network administrator or engineer. It provides a quick and detailed snapshot of the network's state, offering vital insights for troubleshooting, performance monitoring, and security auditing. Its versatility and depth of information make it a staple in network diagnostics and administration.