Why network tools diagnose connectivity in Linux CLI - Challenge Your Understanding

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of the ping command?

You run the command ping -c 3 8.8.8.8 on a Linux terminal. What output do you expect to see?

Linux CLI

ping -c 3 8.8.8.8

A 3 packets transmitted, 0 received, 100% packet loss, time 2002ms

B ping: unknown host 8.8.8.8

C

3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 14.123/15.456/16.789/0.567 ms

D command not found: ping

💡 Hint

Think about what a successful ping to a public DNS server looks like.

The ping command sends ICMP echo requests. If the host is reachable, it replies and shows statistics with packets transmitted and received.

💻 Command Output

intermediate

What does traceroute show about network paths?

You run traceroute example.com. What does the output primarily show?

Linux CLI

traceroute example.com

A A list of routers (hops) between your computer and example.com with their response times

B The IP address of example.com only

C The DNS records of example.com

D The current bandwidth usage of your network

💡 Hint

Traceroute helps you see the path your data takes.

Traceroute sends packets with increasing TTL to discover each hop on the path to the destination, showing latency per hop.

📝 Syntax

advanced

Which command correctly checks open ports on a host?

You want to check if port 80 is open on 192.168.1.1 using netcat (nc). Which command is correct?

A nc -x 192.168.1.1 80

B nc -zv 192.168.1.1 80

C nc -p 80 192.168.1.1

D nc -l 192.168.1.1 80

💡 Hint

Use netcat to scan ports without sending data.

The -z option scans without sending data, and -v enables verbose output. The other options are for listening or invalid.

🔧 Debug

advanced

Why does this ping command fail?

You run ping -c 4 google.com but get the error: ping: unknown host google.com. What is the likely cause?

Linux CLI

ping -c 4 google.com

A The DNS server is unreachable or not configured properly

B The ping command is missing the -c option

C The internet connection is too slow

D The IP address of google.com has changed

💡 Hint

The error means the hostname cannot be resolved.

If DNS cannot resolve the hostname, ping cannot find the IP address to send packets.

🚀 Application

expert

What is the output of this complex network diagnostic script?

Consider this bash script that checks connectivity and logs results:

#!/bin/bash
host=8.8.8.8
if ping -c 2 $host > /dev/null 2>&1; then
  echo "Host $host is reachable"
else
  echo "Host $host is unreachable"
fi

What will be the output if the host is reachable?

Linux CLI

#!/bin/bash
host=8.8.8.8
if ping -c 2 $host > /dev/null 2>&1; then
  echo "Host $host is reachable"
else
  echo "Host $host is unreachable"
fi

A Syntax error near unexpected token `then'

B Host 8.8.8.8 is unreachable

C ping: unknown host 8.8.8.8

D Host 8.8.8.8 is reachable

💡 Hint

The script uses ping and checks its success silently.

The script runs ping quietly and prints reachable if ping succeeds, unreachable otherwise.