Networking Commands

By the end of this lesson you'll be able to diagnose a network from the terminal: check whether a host is up, fetch URLs and download files, see your own IP, find what is listening on a port, resolve domain names, and trace the path packets take.

Learn Networking Commands in our free Command Line course — an interactive lesson with worked examples, a practice exercise and a quick reference.

Part of the free Cli course at LearnCodingFast — hands-on lessons with examples you run in your browser, plus practice exercises and a quick quiz.

What You'll Learn

1. ping: Is the Host Reachable?

ping <host> sends small ICMP echo requests and waits for replies, so it answers two questions at once: can I reach this host , and how fast (the round-trip time ). By default ping keeps going until you press Ctrl+C ; add -c 4 to send exactly four packets and stop. Watch the packet loss line in the summary — 0% is healthy.

2. HTTP from the Terminal: curl & wget

Two tools fetch things over the web. curl <url> prints a URL to the screen — add -I for just the response headers, or -O to save it to a file. wget <url> downloads a file to disk, and wget -O name url sets the output filename. In short: reach for curl to inspect APIs and headers, and wget to download or mirror files.

3. Your Interfaces & IP: ip addr

ip addr (short: ip a ) lists every network interface and the IP addresses assigned to it. lo is loopback (your own machine, 127.0.0.1 ); eth0 / wlan0 is your wired/wireless link with its real address like 192.168.1.42 . On modern Linux this replaces the older ifconfig , which is legacy/deprecated on Linux but still standard on macOS.

4. What's Listening? ss -tuln

When you need to know which service is listening on a port , use ss -tuln . The flags read like a sentence: t = TCP, u = UDP, l = listening, n = numeric (show port numbers instead of names). Scan the Local Address:Port column to find, say, :8080 . The older netstat -tuln does exactly the same job on systems without ss .

5. Resolving Names: dig, nslookup & host

DNS turns a name like example.com into an IP address. Three tools do the lookup: host <domain> gives a one-line answer, nslookup <domain> is the classic tool that also shows the server it asked, and dig <domain> gives the most detailed view. For scripts, dig +short example.com prints just the IP — nothing else.

6. The Path & Remote Access: traceroute & ssh

traceroute <host> (called tracert on Windows) shows every hop — each router between you and the destination — along with how long each takes. It's how you spot where a connection slows down or stops. To actually work on a remote machine, ssh user@host opens a secure shell on it; the dedicated SSH lesson covers keys and config.

7. Ports & /etc/hosts

A port number identifies a specific service on a host: 22 is SSH, 80 is HTTP, 443 is HTTPS, 53 is DNS. So 192.168.1.42:443 means "the HTTPS service on that machine". The /etc/hosts file is a local hostname-to-IP map that the system checks before DNS — perfect for local overrides, like pointing a test name at 127.0.0.1 .

🎯 Your Turn: ping a fixed number of times

Fill in the one blank marked ___ using the # 👉 hint so ping sends a fixed count and stops on its own, then run it and check the Output panel.

🎯 Your Turn: list listening ports

One blank again: combine the four flags (TCP, UDP, listening, numeric) into the right option for ss . Then run it.

Pro Tips

• 💡 Practical recipe: to debug "the site is down", check connectivity ( ping / curl -I ), check what is listening ( ss -tuln ), then resolve the name ( dig / nslookup ).
• 💡 dig +short for scripts: it prints only the IP, so you can drop it straight into a variable or another command.
• 💡 curl prints, wget downloads: remember the split — curl for APIs and headers, wget for saving files to disk.
• 💡 Modern over legacy: prefer ip addr over ifconfig and ss over netstat — same ideas, current tools.

Common Errors (and the fix)

• ping never stops — that's normal: by default it runs forever. Press Ctrl+C to stop, or use ping -c 4 host to send a fixed number.
• "command not found: ifconfig" (or netstat) — these legacy tools may not be installed on modern Linux. Use ip addr and ss -tuln instead.
• ping fails but the website works — many servers block ICMP. A failed ping doesn't always mean "down"; confirm with curl -I https://host .
• "could not resolve host" — a DNS problem, not a connectivity one. Test resolution directly with dig example.com or nslookup example.com .
• "Permission denied" editing /etc/hosts — that file is system-owned. Open it with sudo (e.g. sudo nano /etc/hosts ) to change it.

📋 Quick Reference

Task

Command

Notes

Reachability

ping -c 4 host

Ctrl+C to stop; watch packet loss

Fetch a URL

curl url

-I for headers, -O to save

Download a file

wget url

-O name sets the filename

Interfaces & IPs

ip addr

ip a for short; replaces ifconfig

Listening ports

ss -tuln

or netstat -tuln

Resolve a name

dig +short host

or nslookup / host

Trace the path

traceroute host

tracert on Windows

Remote shell

ssh user@host

Encrypted; see SSH lesson

Common ports

22 / 80 / 443

SSH / HTTP / HTTPS

Local name map

/etc/hosts

Checked before DNS

Frequently Asked Questions

Mini-Challenge: a server health check

No blanks this time — just a brief. Combine what you've learned into a small, repeatable routine that resolves a host, confirms it's reachable, and checks that its web service is responding. Compare your results against the notes in the comments.

🎉 Lesson Complete!

• ✅ ping -c 4 host tests reachability and latency; Ctrl+C stops a running ping
• ✅ curl prints URLs and headers ( -I , -O ); wget downloads files to disk
• ✅ ip addr shows interfaces and IPs (replacing legacy ifconfig ); ss -tuln lists listening ports
• ✅ dig / nslookup / host resolve names; dig +short prints just the IP
• ✅ traceroute shows the path; ports identify services; /etc/hosts overrides DNS locally
• ✅ Next lesson: Advanced Bash Scripting — take your scripts further with arrays, traps, and robust error handling

Practice quiz

Continue this course

• Previous: Scheduling Tasks with cron
• Next: Advanced Bash Scripting

Related lessons

• Lesson 7: Shell Scripting Basics
• SSH lesson