traceroute for path tracing in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this traceroute command?

You run the command traceroute -m 3 example.com. What does the -m 3 option do?

Linux CLI

traceroute -m 3 example.com

A Sends 3 probes per hop instead of the default 1.

B Specifies the port number 3 for traceroute packets.

C Sets the timeout for each probe to 3 seconds.

D Limits the maximum number of hops to 3, so traceroute stops after 3 hops.

💡 Hint

Think about what 'max hops' means in network path tracing.

The -m option sets the maximum number of hops traceroute will probe before stopping. Here, it limits the trace to 3 hops.

💻 Command Output

intermediate

What does this traceroute output indicate?

You run traceroute example.com and see this output for the first hop:

 1  192.168.1.1  1.123 ms  1.045 ms  1.012 ms

What does this line mean?

Linux CLI

traceroute example.com

A The first hop is the router at IP 192.168.1.1, and it responded in about 1 ms each time.

B The traceroute failed to reach the first hop.

C The IP 192.168.1.1 is unreachable.

D The traceroute is showing the destination server's IP.

💡 Hint

The first hop is usually your local router or gateway.

The first hop IP is the first device traceroute reaches, usually your router. The times show how long each probe took.

🔧 Debug

advanced

Why does this traceroute command fail with 'command not found'?

You type traceoute example.com but get bash: traceoute: command not found. What is the problem?

Linux CLI

traceoute example.com

A The domain 'example.com' does not exist.

B You need to run the command as root.

C The command is misspelled; it should be 'traceroute'.

D Traceroute is not installed by default on Linux.

💡 Hint

Check the spelling carefully.

The command is misspelled as 'traceoute' instead of 'traceroute'.

🚀 Application

advanced

How to save traceroute output to a file for later analysis?

You want to run traceroute example.com and save the output to a file named trace.txt. Which command does this correctly?

A All of the above

B traceroute example.com >> trace.txt

C traceroute example.com > trace.txt

D traceroute example.com | tee trace.txt

💡 Hint

Think about how output redirection and tee work.

All options save output to a file: '>' overwrites, '>>' appends, and 'tee' writes and shows output.

🧠 Conceptual

expert

What does an asterisk (*) mean in traceroute output?

In traceroute output, sometimes you see lines like:

 4  * * *

What does this mean?

A The network is blocking traceroute packets permanently.

B The probe timed out; no response was received from that hop.

C Traceroute completed successfully at this hop.

D The hop is the destination server.

💡 Hint

Think about what no response means in network tracing.

Asterisks mean the probe did not get a reply within the timeout period from that hop.

Practice

1. What is the main purpose of the traceroute command in Linux?

easy

A. To display current network connections

B. To list all files in a directory

C. To change the IP address of the system

D. To show the path data takes to reach a destination

Solution

1. Step 1: Understand traceroute function

   The traceroute command traces the route packets take to reach a network host.

2. Step 2: Compare options

   Options A, B, and D describe unrelated commands or functions.

3. Final Answer:

   To show the path data takes to reach a destination -> Option D

4. Quick Check:

   Traceroute purpose = show path [OK]

Hint: Traceroute maps network path hops quickly [OK]

Common Mistakes:

• Confusing traceroute with ping
• Thinking traceroute changes network settings
• Mixing traceroute with file commands

2. Which of the following is the correct syntax to run traceroute to example.com with a maximum of 5 hops?

easy

A. traceroute -m 5 example.com

B. traceroute -max 5 example.com

C. traceroute --maxhops=5 example.com

D. traceroute -h 5 example.com

Solution

1. Step 1: Recall traceroute max hops option

   The option -m sets the max number of hops in traceroute.

2. Step 2: Check syntax correctness

   Only traceroute -m 5 example.com uses the correct option and format.

3. Final Answer:

   traceroute -m 5 example.com -> Option A

4. Quick Check:

   Max hops option = -m [OK]

Hint: Use -m to limit hops in traceroute [OK]

Common Mistakes:

• Using -max or --maxhops which are invalid
• Confusing -h (help) with hop limit
• Placing options after the hostname

3. What will be the output of the command traceroute -n 8.8.8.8?

medium

A. It shows an error because -n is invalid

B. It shows the route to 8.8.8.8 with hostnames only, no IP addresses

C. It shows the route to 8.8.8.8 with IP addresses only, no hostnames

D. It shows the route with both hostnames and IP addresses

Solution

1. Step 1: Understand the -n option in traceroute

   The -n option disables hostname resolution and shows IP addresses only.

2. Step 2: Analyze output format

   Therefore, the output will list IP addresses without hostnames.

3. Final Answer:

   It shows the route to 8.8.8.8 with IP addresses only, no hostnames -> Option C

4. Quick Check:

   -n means no hostname lookup [OK]

Hint: -n shows IPs only, no names [OK]

Common Mistakes:

• Thinking -n shows hostnames
• Assuming -n causes error
• Expecting both IP and hostname with -n

4. You run traceroute -m 3 example.com but it shows more than 3 hops. What is the likely cause?

medium

A. The -m option was ignored because of a syntax error

B. Traceroute always shows all hops regardless of -m

C. The command is correct; traceroute shows up to 3 hops only

D. The hostname resolves to multiple IPs causing extra hops

Solution

1. Step 1: Check syntax of the command

   The correct syntax requires a space between -m and the number, so -m 3 is correct.

2. Step 2: Consider possible syntax errors

   If the option was typed incorrectly (like -m3 without space), traceroute may ignore it and show default hops.

3. Step 3: Evaluate other options

   Traceroute does not always ignore -m; it respects it if syntax is correct. Multiple IPs do not increase hops count.

4. Final Answer:

   The -m option was ignored because of a syntax error -> Option A

5. Quick Check:

   Syntax error causes option ignore [OK]

Hint: Check option syntax carefully for -m [OK]

Common Mistakes:

• Using -m3 without space causing ignore
• Assuming traceroute ignores -m always
• Confusing hops with IP resolution count

5. You want to trace the path to example.com but skip hostname lookups and limit hops to 4. Which command achieves this?

hard

A. traceroute -m 4 -h example.com

B. traceroute -n -m 4 example.com

C. traceroute --no-hostname --max-hops=4 example.com

D. traceroute -4 -n example.com

Solution

1. Step 1: Identify options for skipping hostname and limiting hops

   -n skips hostname lookup; -m 4 limits hops to 4.

2. Step 2: Verify option correctness and order

   traceroute -n -m 4 example.com uses both correctly. traceroute -m 4 -h example.com uses invalid -h. traceroute --no-hostname --max-hops=4 example.com uses non-standard options. traceroute -4 -n example.com limits to IPv4 but not hops.

3. Final Answer:

   traceroute -n -m 4 example.com -> Option B

4. Quick Check:

   -n and -m 4 combined = correct command [OK]

Hint: Combine -n and -m for no hostname and hop limit [OK]

Common Mistakes:

• Using -h instead of -m for hops
• Assuming --no-hostname is valid
• Confusing -4 (IPv4) with hop limit