Quick Answer
The answer is to perform MAC flooding to cause the switch to fail open. This command uses the macof tool to generate a massive number of frames, each with a unique, fake source MAC address, which rapidly fills the switch’s Content Addressable Memory (CAM) table. Once the CAM table overflows, the switch can no longer store legitimate MAC-to-port mappings and enters a fail-open state, effectively broadcasting all traffic to every port like a hub, thereby enabling packet sniffing. On the Certified Ethical Hacker CEH exam, this concept tests your understanding of Layer 2 attacks and switch security; a common trap is confusing MAC flooding with ARP poisoning, but remember that macof targets the CAM table, not the ARP cache. A useful memory tip: “macof floods the CAM, making a switch act like a hub—fail open for sniffing.”
This CEH practice question tests your understanding of malware, social engineering and network attacks. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
During a penetration test, you run the command: 'macof -i eth0 -s 192.168.1.1 -d 192.168.2.1 -e 00:11:22:33:44:55'. What is the intended effect of this command?
Execute a SYN flood against the target
Why wrong: SYN flood is done with tools like hping3, not macof.
Perform MAC flooding to cause switch to fail open
macof floods with random MACs to exhaust CAM table, enabling sniffing.
Perform ARP poisoning
Why wrong: ARP poisoning uses ARP replies; macof generates random MAC addresses.
Spoof DNS responses
Why wrong: DNS spoofing is done with tools like dnsspoof, not macof.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Perform MAC flooding to cause switch to fail open
macof is a tool used for MAC flooding, which floods a switch with fake MAC addresses to overflow the CAM table, causing the switch to fail open and operate like a hub, allowing packet sniffing.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Execute a SYN flood against the target
Why it's wrong here
SYN flood is done with tools like hping3, not macof.
Perform MAC flooding to cause switch to fail open
Why this is correct
macof floods with random MACs to exhaust CAM table, enabling sniffing.
Related concept
Read the scenario before looking for a memorised answer.
Perform ARP poisoning
Why it's wrong here
ARP poisoning uses ARP replies; macof generates random MAC addresses.
Spoof DNS responses
Why it's wrong here
DNS spoofing is done with tools like dnsspoof, not macof.
Common exam traps
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the CEH exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Identify which CEH exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Malware, Social Engineering and Network Attacks — This question tests Malware, Social Engineering and Network Attacks — Read the scenario before looking for a memorised answer..
The correct answer is: Perform MAC flooding to cause switch to fail open — macof is a tool used for MAC flooding, which floods a switch with fake MAC addresses to overflow the CAM table, causing the switch to fail open and operate like a hub, allowing packet sniffing.
Identify which CEH exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Read the scenario before looking for a memorised answer.
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Same concept, more angles
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A penetration tester runs the following command: `macof -i eth0 -s 192.168.1.100 -d 10.0.0.1`. Which attack is being performed?
hardWhy C: Macof is a tool used for MAC flooding, which fills the switch's CAM table with fake MAC addresses, causing it to fail open and broadcast traffic to all ports.
Last reviewed: Jun 21, 2026
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