The answer is ARP spoofing. This is correct because the attack involves an attacker sending forged ARP replies to link their own MAC address with the default gateway’s IP, poisoning the victim’s ARP cache and redirecting traffic meant for the gateway to the attacker for man-in-the-middle interception. On the Security+ SY0-701 exam, this scenario tests your ability to distinguish between local network attacks (ARP spoofing) and DNS-level attacks (DNS poisoning), which target name resolution rather than MAC-to-IP mappings. A common trap is confusing the two because both involve cache poisoning, but remember: ARP spoofing operates at Layer 2 on the local subnet, while DNS poisoning corrupts DNS resolver caches at Layer 7. For a quick memory tip, think “ARP = Address Resolution Protocol = local MAC trickery” versus “DNS = Domain Name System = domain name hijacking.”
SY0-701 Threats, Vulnerabilities, and Mitigations Practice Question
This SY0-701 practice question tests your understanding of threats, vulnerabilities, and mitigations. 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.
Exhibit
Host 192.0.2.45 arp -a
Internet Address Physical Address Type
192.0.2.1 00-50-56-a1-b2-c3 dynamic
192.0.2.1 00-50-56-a1-b2-c4 dynamic
Packet capture:
10:14:02 ARP Reply: 192.0.2.1 is-at 00:50:56:a1:b2:c4
10:14:03 ARP Reply: 192.0.2.1 is-at 00:50:56:a1:b2:c4
10:14:05 Gateway traffic is briefly forwarded to 192.0.2.200
Switch CAM table:
Gi1/0/7 00:50:56:a1:b2:c4
Gi1/0/24 00:50:56:a1:b2:c4
Based on the exhibit, which attack is most likely occurring on the local network?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Host 192.0.2.45 arp -a
Internet Address Physical Address Type
192.0.2.1 00-50-56-a1-b2-c3 dynamic
192.0.2.1 00-50-56-a1-b2-c4 dynamic
Packet capture:
10:14:02 ARP Reply: 192.0.2.1 is-at 00:50:56:a1:b2:c4
10:14:03 ARP Reply: 192.0.2.1 is-at 00:50:56:a1:b2:c4
10:14:05 Gateway traffic is briefly forwarded to 192.0.2.200
Switch CAM table:
Gi1/0/7 00:50:56:a1:b2:c4
Gi1/0/24 00:50:56:a1:b2:c4
A
DNS cache poisoning
Why wrong: DNS poisoning targets name resolution records, not Ethernet-layer ARP mappings on a local subnet.
B
ARP spoofing
The host receives repeated ARP replies claiming the gateway IP belongs to a different MAC address, and the same MAC appears on multiple switch ports. That combination indicates ARP spoofing or poisoning, which can redirect traffic through an attacker for interception or disruption. The brief forwarding to another IP is consistent with a man-in-the-middle attempt built on forged ARP replies.
C
Replay attack
Why wrong: Replay attacks reuse captured valid messages, typically in authentication or protocol exchanges, rather than altering ARP ownership mappings.
D
Amplification denial-of-service
Why wrong: Amplification uses small requests to trigger much larger responses, usually in distributed volumetric flooding attacks.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ARP spoofing
ARP spoofing is the most likely attack because the exhibit shows an attacker sending forged ARP replies to associate the attacker's MAC address with the IP address of the default gateway. This poisons the ARP cache of the victim, causing all traffic destined for the gateway to be sent to the attacker instead, enabling man-in-the-middle interception.
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.
✗
DNS cache poisoning
Why it's wrong here
DNS poisoning targets name resolution records, not Ethernet-layer ARP mappings on a local subnet.
✓
ARP spoofing
Why this is correct
The host receives repeated ARP replies claiming the gateway IP belongs to a different MAC address, and the same MAC appears on multiple switch ports. That combination indicates ARP spoofing or poisoning, which can redirect traffic through an attacker for interception or disruption. The brief forwarding to another IP is consistent with a man-in-the-middle attempt built on forged ARP replies.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Replay attack
Why it's wrong here
Replay attacks reuse captured valid messages, typically in authentication or protocol exchanges, rather than altering ARP ownership mappings.
✗
Amplification denial-of-service
Why it's wrong here
Amplification uses small requests to trigger much larger responses, usually in distributed volumetric flooding attacks.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse ARP spoofing with DNS cache poisoning because both involve 'poisoning' a cache, but ARP operates at Layer 2 (MAC addresses) while DNS operates at Layer 7 (domain name resolution).
Detailed technical explanation
How to think about this question
ARP spoofing exploits the stateless nature of ARP; hosts accept unsolicited ARP replies without verification. Tools like arpspoof or Ettercap send gratuitous ARP packets to update the target's ARP cache. In a real-world scenario, an attacker could use ARP spoofing to perform session hijacking, sniffing credentials, or launching a denial-of-service by dropping forwarded packets.
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 security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this SY0-701 question in full detail.
Threats, Vulnerabilities, and Mitigations — This question tests Threats, Vulnerabilities, and Mitigations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: ARP spoofing — ARP spoofing is the most likely attack because the exhibit shows an attacker sending forged ARP replies to associate the attacker's MAC address with the IP address of the default gateway. This poisons the ARP cache of the victim, causing all traffic destined for the gateway to be sent to the attacker instead, enabling man-in-the-middle interception.
What should I do if I get this SY0-701 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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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. Based on the exhibit, what network attack is most likely occurring on the office LAN?
medium
✓ A.ARP poisoning, because a rogue system is sending false layer 2 address mappings.
B.Replay attack, because the same ARP reply appears multiple times.
C.Denial of service, because users notice certificate warnings.
D.DNS poisoning, because the users cannot reach internal sites cleanly.
Why A: ARP poisoning is the correct answer because the exhibit shows a rogue system sending unsolicited ARP replies that map the gateway's IP address to the attacker's MAC address. This causes traffic destined for the gateway to be redirected to the attacker, enabling man-in-the-middle interception. The attack exploits the lack of authentication in ARP, allowing false layer 2 address mappings to corrupt the ARP cache of other hosts on the LAN.
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Question Discussion
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