The answer is that multiple IP addresses mapping to the same MAC address is a definitive sign of ARP spoofing. This occurs because an attacker sends forged ARP replies to poison the target’s ARP cache, associating their own MAC address with the IP of a legitimate host like the default gateway. As a result, any traffic destined for that gateway IP is redirected to the attacker’s MAC, creating a detectable mismatch between the expected IP-to-MAC binding and the actual network traffic. On the Cisco CyberOps Associate 200-201 exam, this concept tests your ability to identify cache poisoning behaviors in packet captures, often appearing alongside questions about man-in-the-middle attacks. A common trap is confusing duplicate IPs with duplicate MACs—remember, the attacker’s goal is to hijack traffic by claiming multiple IPs under one MAC, not the reverse. For a quick memory tip, think “one MAC, many IPs” as the red flag for ARP spoofing.
200-201 Network Intrusion Analysis Practice Question
This 200-201 practice question tests your understanding of network intrusion analysis. 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.
Which TWO network behaviors suggest an ARP spoofing attack is occurring? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Packets originating from a MAC address that does not match the IP's legitimate MAC
Option C is correct because in an ARP spoofing attack, the attacker sends forged ARP replies that associate their own MAC address with the IP address of a legitimate host (e.g., the default gateway). This causes packets destined for that IP to be sent to the attacker's MAC, creating a mismatch between the source MAC in the packet and the legitimate MAC address for that IP. Detecting such mismatches is a key indicator of ARP cache poisoning.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
Packets originating from a MAC address that does not match the IP's legitimate MAC
Why this is correct
Indicates the attacker is sending packets with a spoofed MAC.
Related concept
Read the scenario before looking for a memorised answer.
✗
An increase in broadcast ARP traffic
Why it's wrong here
Can be normal or scanning.
✓
Multiple IP addresses mapping to the same MAC address
Why this is correct
The attacker uses one MAC to impersonate multiple IPs.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between normal ARP traffic (e.g., broadcasts for resolution) and malicious ARP behavior (e.g., multiple IPs on one MAC or MAC-IP mismatches), so candidates mistakenly choose high ARP volume or TCP RSTs as spoofing indicators.
Detailed technical explanation
How to think about this question
ARP spoofing exploits the stateless nature of ARP, where hosts accept unsolicited ARP replies without verification. Tools like `arpspoof` or `ettercap` send forged gratuitous ARP replies to poison the target's ARP cache, redirecting traffic through the attacker for man-in-the-middle attacks. Defenses include dynamic ARP inspection (DAI) on switches, which validates ARP packets against a DHCP snooping binding table, and static ARP entries for critical hosts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Intrusion Analysis — This question tests Network Intrusion Analysis — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Packets originating from a MAC address that does not match the IP's legitimate MAC — Option C is correct because in an ARP spoofing attack, the attacker sends forged ARP replies that associate their own MAC address with the IP address of a legitimate host (e.g., the default gateway). This causes packets destined for that IP to be sent to the attacker's MAC, creating a mismatch between the source MAC in the packet and the legitimate MAC address for that IP. Detecting such mismatches is a key indicator of ARP cache poisoning.
What should I do if I get this 200-201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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