mediumMultiple Choice
350-401 Practice Question: Runs the following command on Router R6: R6# show…
A network engineer runs the following command on Router R6:
R6# show ip dhcp conflict IP address Detection method Detection time VRF 10.0.0.10 Ping Mar 01 2025 10:00 AM default 10.0.0.15 Gratuitous ARP Mar 01 2025 10:05 AM default
Based on this output, what can be concluded?
⚠ Common exam trap
Cisco often tests the misconception that a DHCP conflict log shows successfully assigned addresses, when in fact it shows addresses that the server detected as already in use and therefore excluded from assignment.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The addresses 10.0.0.10 and 10.0.0.15 are unavailable for DHCP assignment.
The output shows two IP addresses that have been detected as conflicting with other devices on the network. When a DHCP server detects a conflict (via ping or gratuitous ARP), it marks those addresses as unavailable and will not assign them to new clients. Therefore, 10.0.0.10 and 10.0.0.15 are excluded from the DHCP pool until the conflicts are cleared by an administrator.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The DHCP server has successfully assigned these addresses to clients.
Why it's wrong here
A DHCP server first probes every candidate address with ping and gratuitous ARP before offering it. Because both 10.0.0.10 and 10.0.0.15 appear in the conflict table, those addresses had active responses during probing, so they were never successfully assigned or leased to any client. Conflict entries represent withheld addresses, not completed assignments.
- ✓
The addresses 10.0.0.10 and 10.0.0.15 are unavailable for DHCP assignment.
Why this is correct
When an address is logged as a conflict, the DHCP server removes it from the normal allocation pool and will not offer it in future DISCOVER messages until the conflict is explicitly cleared. Both 10.0.0.10 and 10.0.0.15 remain in this conflicted state, making them permanently unavailable for DHCP assignment unless an administrator runs 'clear ip dhcp conflict' or removes the entries. This exclusion prevents the server from duplicating addresses already in use elsewhere.
- ✗
The DHCP server uses only ping to detect conflicts.
Why it's wrong here
Cisco IOS DHCP servers do not depend on ping alone for conflict detection; they also use gratuitous ARP probes to see if an address is already claimed on the local segment. The presence of both detection mechanisms means the statement 'uses only ping' is false, even though ping may be the more visible method. ICMP echo probes can be blocked by firewalls, so the ARP check provides an additional layer of certainty.
- ✗
The conflicts were caused by the DHCP server itself.
Why it's wrong here
The conflict table entry is generated when the server's own probe receives a reply from another device using that IP, not from the server's own protocol stack. If the DHCP server itself caused the conflict, the address would be in use by the server's interface, but the server is simply detecting an outside responder. Therefore, these conflicts typically indicate a static host, a rogue DHCP server, or a misconfigured endpoint is already using the address.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.