Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
During troubleshooting, several hosts in VLAN 20 lose access to the default gateway at random. Their ARP caches now map the gateway IP to a workstation MAC address, and traffic briefly flows through that workstation before timing out. What attack is most likely?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Distractor review
DNS poisoning, because the workstation name may be resolving to the wrong IP address.
DNS poisoning affects name resolution records, but the symptom here is an ARP cache mapping the gateway IP to the wrong MAC address on the local network.
B
Best answer
ARP poisoning, because false ARP replies are redirecting gateway traffic to another host.
ARP poisoning fits exactly when a host sends falsified ARP information so victims associate the gateway IP with the attacker’s MAC address. That can enable interception, disruption, or man-in-the-middle behavior on the local subnet.
C
Distractor review
Replay attack, because the attacker is reusing old network frames to confuse the hosts.
Replay attacks involve captured traffic being resent later. The clue here is a poisoned ARP table, not the reuse of valid packets or timestamps.
D
Distractor review
Denial of service, because traffic eventually times out and connectivity is lost.
DoS can cause outages, but the explicit evidence of wrong ARP mappings identifies the mechanism. The timeout is a result of the poisoning, not the root cause itself.
Common exam trap
Common exam trap: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Technical deep dive
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
- Access ports place end devices into a single VLAN.
- Trunk ports carry multiple VLANs between switches.
- Allowed VLAN lists decide which VLANs can cross a trunk.
- Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
- Use show vlan brief to verify access VLANs.
- Use show interfaces trunk to verify trunk state and allowed VLANs.
- Do not treat every same-VLAN issue as a routing problem.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A laptop is suspected of being used in a malware incident. It is still powered on and connected to Wi-Fi. What should the responder do before shutting it down?
Question 2
An employee reports a ransomware note on a file server. The server is still powered on, shares are still being accessed, and management wants service restored as quickly as possible. What should the incident response team do first?
Question 3
An employee reports a ransomware note on a finance laptop. The laptop is still powered on, connected to Wi-Fi, and the user says they were just working in a spreadsheet. Management wants the fastest safe response that also preserves evidence. What should the responder do first?
Question 4
You are handed a company laptop suspected in an insider theft case. Legal says the evidence may be needed in court. Which action best preserves admissibility?
Question 5
A developer wants to reduce the risk of SQL injection in a new customer search form. Which two changes are the best mitigations? Select two.
Question 6
A branch office uses a flat LAN, and a compromise on one user workstation could spread quickly to finance systems. Management wants finance workstations isolated from general users, but finance staff still need access to a central finance application and network printer. What is the best design change?
FAQ
Questions learners often ask
What does this SY0-701 question test?
Access ports place end devices into a single VLAN.
What is the correct answer to this question?
The correct answer is: ARP poisoning, because false ARP replies are redirecting gateway traffic to another host. — ARP poisoning is the correct answer because the victims are learning a false IP-to-MAC mapping for the default gateway. That causes traffic to be sent to the wrong workstation, which can intercept, alter, or drop packets. The local subnet behavior and ARP cache evidence are the key indicators that distinguish this from DNS issues or generic outages. Why others are wrong: DNS poisoning would change name-to-IP resolution, not the gateway IP-to-MAC entries in ARP tables. Replay attacks rely on captured traffic being resent and do not directly explain the cache poisoning evidence. A denial of service describes the effect of lost connectivity, but here the mechanism is specifically malicious ARP responses.
What should I do if I get this SY0-701 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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