traceroute for path tracing in Linux CLI - Mini Project: Build & Apply

Traceroute for Path Tracing

📖 Scenario: You want to find the path your data takes to reach a website. This helps you understand how your internet connection travels through different servers.

🎯 Goal: Build a simple script that uses traceroute to trace the path to a website and shows the result.

📋 What You'll Learn

Use the traceroute command to trace the path to example.com

Store the target website in a variable called target

Use a variable called max_hops to limit the number of hops to 5

Run traceroute with the -m option using max_hops

Print the traceroute output

💡 Why This Matters

🌍 Real World

Network administrators and users use traceroute to diagnose network paths and delays.

💼 Career

Understanding traceroute helps in troubleshooting network issues and improving connectivity.

1

Set the target website

Create a variable called target and set it to the string example.com.

Linux CLI

# Create a variable called target and set it to 'example.com'
target="example.com"

Hint

Use target="example.com" to store the website.

2

Set the maximum hops

Create a variable called max_hops and set it to the number 5.

Linux CLI

target="example.com"
# Create a variable called max_hops and set it to 5
max_hops=5

Hint

Use max_hops=5 to limit the hops.

3

Run traceroute with max hops

Write a command that runs traceroute with the -m option set to max_hops and the target set to target. Use command substitution to store the output in a variable called result.

Linux CLI

target="example.com"
max_hops=5
# Run traceroute with -m max_hops and target, store output in result
result=$(traceroute -m $max_hops $target)

Hint

Use result=$(traceroute -m $max_hops $target) to run traceroute and save output.

4

Print the traceroute result

Print the contents of the variable result to show the traceroute output.

Linux CLI

target="example.com"
max_hops=5
result=$(traceroute -m $max_hops $target)
# Print the traceroute result
printf "%s\n" "$result"

Hint

Use printf "%s\n" "$result" to print the output.

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