Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
After a switch reboot in a conference room, several laptops obtain valid IP addresses in the correct subnet, but their default gateway changes to 10.20.40.50, which is not the legitimate router. Packet capture shows DHCP offers coming from a MAC address that does not belong to the approved DHCP server, and the rogue device responds faster than the real server. What attack is most likely occurring?
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
ARP poisoning, because the attacker is changing IP-to-MAC mappings on the local network.
ARP poisoning targets address resolution between IP and MAC addresses. This scenario is about fake DHCP offers and an incorrect gateway assignment, which occurs before ARP is involved.
B
Best answer
Rogue DHCP service, because an unauthorized DHCP server is handing out network settings.
A rogue DHCP service is the best answer. The clients receive valid-looking leases from an unauthorized device, and the device supplies the default gateway before the legitimate server can respond. This is a common and dangerous network attack because it can redirect traffic, enable interception, or break connectivity without requiring packet spoofing at the ARP layer.
C
Distractor review
Replay attack, because the attacker is reusing old DHCP offers.
Replay attacks involve capturing and retransmitting valid traffic. The scenario instead points to a live unauthorized DHCP responder, not a reused historical packet set.
D
Distractor review
DNS poisoning, because the clients are being sent to the wrong network path.
DNS poisoning alters name resolution to misdirect clients to malicious hostnames or addresses. Here the wrong default gateway is being assigned directly by a fake DHCP server, so the issue is earlier in the network configuration process.
Common exam trap
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Technical deep dive
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
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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?
CIDR notation defines the prefix length.
What is the correct answer to this question?
The correct answer is: Rogue DHCP service, because an unauthorized DHCP server is handing out network settings. — A rogue DHCP service is most likely. The laptops are receiving legitimate-looking lease information from an unauthorized device, and the incorrect default gateway is proof that the rogue server is influencing network configuration. Because DHCP responses are often accepted based on speed, a rogue server that answers first can redirect traffic or cause outages before defenders notice. This is a classic rogue service problem. Why others are wrong: ARP poisoning changes layer-2 address mappings, but the evidence here is about DHCP offers and gateway assignment. Replay attacks reuse captured traffic, but the scenario describes a live unauthorized responder. DNS poisoning would tamper with hostname resolution, not directly provide a false default gateway via DHCP.
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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