- A
Configure a static IP address on the DHCP server to ensure it is always reachable.
Why wrong: The DHCP server is already reachable and has available addresses; the problem is that DHCP broadcasts from clients in VLAN 20 are not reaching the server.
- B
Configure the 'ip helper-address 192.168.10.5' command on the router interface GigabitEthernet0/1.20.
The ip helper-address command enables the router to forward DHCP broadcasts as unicasts to the specified DHCP server, allowing clients in VLAN 20 to obtain IP addresses from the remote server.
- C
Enable DHCP snooping globally on the switch SW1.
Why wrong: DHCP snooping is a security feature that filters untrusted DHCP messages; it does not relay DHCP broadcasts across subnets.
- D
Increase the DHCP lease time on the server to 30 days.
Why wrong: The lease time affects how long clients keep their IP addresses, but it does not enable DHCP broadcasts to cross subnets.
Quick Answer
The correct answer is to configure the 'ip helper-address 192.168.10.5' command on the router interface GigabitEthernet0/1.20. This is necessary because DHCP relies on broadcast discovery messages, and routers by default do not forward broadcasts across subnets; the ip helper-address command converts the broadcast into a unicast and relays it to the specified DHCP server, enabling hosts in VLAN 20 to obtain an IP address from the server at 192.168.10.5. On the CCNA 200-301 v2 exam, this scenario tests your understanding of DHCP relay configuration and the fact that a DHCP server and its clients must be on the same subnet unless a relay agent is used. A common trap is thinking that a static route or a VLAN change will fix the issue, but the core problem is broadcast isolation. Remember the memory tip: "Helper helps the broadcast hop across the router"—if the server is not local, you must relay.
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A network administrator is troubleshooting a new branch office where hosts in VLAN 20 on switch SW1 cannot obtain IP addresses from the DHCP server located at 192.168.10.5 in the main data center. The router R1 is configured as the default gateway for VLAN 20 with interface GigabitEthernet0/1.20. The administrator verifies that the DHCP server is reachable and has available addresses. What configuration change should the administrator make to resolve the issue?
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
Configure the 'ip helper-address 192.168.10.5' command on the router interface GigabitEthernet0/1.20.
The correct answer is B because the DHCP server is on a different subnet than the hosts in VLAN 20. By default, DHCP broadcasts are not forwarded across routers. The 'ip helper-address 192.168.10.5' command on the router's subinterface GigabitEthernet0/1.20 converts the broadcast DHCP request into a unicast and forwards it to the DHCP server, allowing the hosts to obtain IP addresses.
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.
- ✗
Configure a static IP address on the DHCP server to ensure it is always reachable.
- ✓
Configure the 'ip helper-address 192.168.10.5' command on the router interface GigabitEthernet0/1.20.
- ✗
Enable DHCP snooping globally on the switch SW1.
Why it's wrong here
DHCP snooping is a security feature that filters untrusted DHCP messages; it does not relay DHCP broadcasts across subnets.
- ✗
Increase the DHCP lease time on the server to 30 days.
Why it's wrong here
The lease time affects how long clients keep their IP addresses, but it does not enable DHCP broadcasts to cross subnets.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Configure the 'ip helper-address 192.168.10.5' command on the router interface GigabitEthernet0/1.20.Correct answer▾
Why this is correct
The ip helper-address command enables the router to forward DHCP broadcasts as unicasts to the specified DHCP server, allowing clients in VLAN 20 to obtain IP addresses from the remote server.
✗Configure a static IP address on the DHCP server to ensure it is always reachable.Wrong answer — click to see why▾
Why this is wrong here
A static IP on the server does not forward broadcasts across subnets; the server's reachability is not the issue.
✗Enable DHCP snooping globally on the switch SW1.Wrong answer — click to see why▾
Why this is wrong here
Enabling DHCP snooping without proper configuration could block legitimate DHCP traffic, and it does not solve the broadcast forwarding issue.
✗Increase the DHCP lease time on the server to 30 days.Wrong answer — click to see why▾
Why this is wrong here
The problem is not about lease duration; clients cannot receive any DHCP offers because broadcasts are not forwarded.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that DHCP issues across subnets are caused by server availability or switch security features, when the real problem is the lack of a DHCP relay agent (ip helper-address) on the router interface facing the client VLAN.
Detailed technical explanation
How to think about this question
The 'ip helper-address' command uses DHCP relay agent functionality defined in RFC 1542 (BOOTP/DHCP relay). When a router receives a DHCP broadcast on an interface with this command, it creates a unicast DHCP packet with the gateway IP address (giaddr) set to the router's interface IP, so the DHCP server knows which subnet to assign an address from. In a real-world scenario, if multiple VLANs need DHCP, you would configure the helper address on each subinterface, and the server must have scopes for each subnet.
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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Network Services and Security — study guide chapter
Learn the concepts, then practise the questions
- →
Network Services and Security practice questions
Targeted practice on this topic area only
- →
All 200-301 questions
1,819 questions across all exam domains
- →
CCNA 200-301 v2 study guide
Full concept coverage aligned to exam objectives
- →
200-301 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related 200-301 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Network Infrastructure and Connectivity practice questions
Practise 200-301 questions linked to Network Infrastructure and Connectivity.
Switching and Network Access practice questions
Practise 200-301 questions linked to Switching and Network Access.
IP Routing practice questions
Practise 200-301 questions linked to IP Routing.
Network Services and Security practice questions
Practise 200-301 questions linked to Network Services and Security.
AI and Network Operations practice questions
Practise 200-301 questions linked to AI and Network Operations.
CCNA subnetting practice questions
Practise IPv4 subnetting, CIDR, masks, host ranges and subnet selection.
CCNA OSPF practice questions
Practise OSPF neighbours, router IDs, metrics, areas and routing-table interpretation.
CCNA VLAN practice questions
Practise VLANs, access ports, trunks, allowed VLANs and switching scenarios.
CCNA STP practice questions
Practise spanning tree, root bridge election, port roles and STP troubleshooting.
CCNA EtherChannel practice questions
Practise LACP, PAgP, port-channel behaviour and bundle requirements.
CCNA ACL practice questions
Practise standard and extended ACLs, permit/deny logic and traffic filtering.
CCNA NAT practice questions
Practise static NAT, dynamic NAT, PAT and inside/outside address translation.
Practice this exam
Start a free 200-301 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this 200-301 question test?
Network Services and Security — This question tests Network Services and Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure the 'ip helper-address 192.168.10.5' command on the router interface GigabitEthernet0/1.20. — The correct answer is B because the DHCP server is on a different subnet than the hosts in VLAN 20. By default, DHCP broadcasts are not forwarded across routers. The 'ip helper-address 192.168.10.5' command on the router's subinterface GigabitEthernet0/1.20 converts the broadcast DHCP request into a unicast and forwards it to the DHCP server, allowing the hosts to obtain IP addresses.
What should I do if I get this 200-301 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 11, 2026
This 200-301 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 200-301 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.