Essential Linux Networking Commands for DevOps Engineers

Networking is crucial in DevOps. Knowing commands like netstat, ifconfig, and iptables lets you quickly troubleshoot and secure connections. Here’s a 1-minute guide to mastering these commands!

Key Commands & Quick Uses

1. netstat

   • netstat -an: Lists all active connections and ports great for spotting open connections.

   • netstat -tuln: Shows TCP/UDP ports in use, useful for confirming active services.

2. ifconfig

   • ifconfig eth0: Displays IP, netmask, and MAC confirm interface settings.

   • sudo ifconfig eth0 down/up: Resets the network interface, helpful for troubleshooting.

   • Set IP: sudo ifconfig eth0 192.168.1.10 netmask 255.255.255.0 to assign a static IP.

3. iptables

   • sudo iptables -L: Lists all firewall rules, quickly shows allowed/blocked traffic.

   • Block IP: sudo iptables -A INPUT -s 192.168.1.5 -j DROP blocks incoming traffic from a specific IP.

   • Open Port 80: sudo iptables -A INPUT -p tcp --dport 80 -j ACCEPT allows HTTP traffic for web servers.

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Interview Questions

1. What does netstat -an do?
   Lists all active connections, great for spotting open or unused ports.

2. Why use ifconfig to bring down an interface?
   To reset its connection or apply new configurations easily.

3. How to allow SSH in iptables?
   sudo iptables -A INPUT -p tcp --dport 22 -j ACCEPT opens port 22 for secure access.