Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A security analyst has enabled DHCP snooping on all VLANs of the company's switches to mitigate the risk of rogue DHCP servers. After implementation, the analyst discovers that clients are still receiving IP addresses from an unauthorized DHCP server. The unauthorized server is connected to a switch port that is currently configured as a trusted port. What should the analyst do to stop the rogue DHCP server from offering addresses?
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
Enable Dynamic ARP Inspection on the VLAN.
Dynamic ARP Inspection validates ARP packets, not DHCP messages. It does not prevent a rogue DHCP server from offering addresses on a trusted port.
B
Best answer
Change the port connecting the unauthorized server to an untrusted port.
DHCP snooping treats trusted ports as authorized sources of DHCP offers. By making the port untrusted, the switch will drop any DHCP server messages received on that port.
C
Distractor review
Configure port security on the unauthorized server's port to limit MAC addresses.
Port security restricts the number of MAC addresses on a port but does not filter DHCP messages. The rogue server could still issue DHCP offers.
D
Distractor review
Increase the rate limit on the unauthorized server's port.
Rate limiting controls the amount of traffic, not the type of traffic. It would not prevent the rogue server from sending DHCP offers.
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 network engineer needs to connect two switches located 400 meters apart. The cable run includes high electromagnetic interference from nearby machinery. The engineer decides to use fiber optic cabling. Which transceiver type and fiber combination should be used to ensure the link reaches 400 meters while remaining cost-effective?
Question 2
A network engineer is designing a new switched network and needs to ensure that broadcast traffic from one department does not reach another department's workstations. The engineer plans to use VLANs. Which of the following must be configured on the switches to isolate broadcast domains as intended?
Question 3
A security engineer is configuring a site-to-site VPN between two branch offices. The requirement is to encrypt all traffic between the two networks using IPsec. Which IPsec mode should be used to encrypt the entire IP packet including the original header?
Question 4
A network administrator is connecting two switches to increase bandwidth and provide redundancy. Which technology should be used to combine multiple physical links into a single logical link?
Question 5
A network administrator is experiencing issues where unauthorized devices are offering IP addresses to clients, causing connectivity problems. Which security feature should be enabled on switches to prevent this?
Question 6
A network administrator is troubleshooting a connectivity issue and suspects the problem is related to the physical cabling. At which layer of the OSI model should the administrator begin their investigation?
FAQ
Questions learners often ask
What does this N10-009 question test?
Access ports place end devices into a single VLAN.
What is the correct answer to this question?
The correct answer is: Change the port connecting the unauthorized server to an untrusted port. — DHCP snooping filters DHCP messages based on port trust states. Only trusted ports are allowed to send DHCP offer and DHCP ACK messages. If the rogue server is connected to a trusted port, it will be allowed to respond to DHCP requests. The analyst must configure the port as untrusted so that the switch ignores or drops DHCP server messages from that port. Option B is correct. Options A, C, and D do not address the root cause.
What should I do if I get this N10-009 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
Discussion
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