- A
The DHCP relay agent is not configured to use the VRF GUEST; the ip helper-address command must be applied under the VRF interface, but the DHCP server is in a different VRF, requiring inter-VRF routing or the use of the ip dhcp relay information option.
Why wrong: Incorrect because the helper-address is applied on the interface in the GUEST VRF; the issue is that the relay cannot forward to a server in a different VRF without route leaking.
- B
The DHCP server is in a different VRF, and the switch does not have a route from the GUEST VRF to the CORP VRF for the DHCP server.
Correct because DHCP relay forwards the request based on the routing table of the source VRF. Without a route to the server in the GUEST VRF, the relay fails.
- C
The DHCP server is not configured with a scope for the guest subnet.
Why wrong: Incorrect because this would cause the server to not respond, but the relay might still forward the request; the issue is that the request never reaches the server.
- D
The guest VRF is missing the ip dhcp relay command globally.
Why wrong: Incorrect because DHCP relay is enabled by default; the global command is not required.
CCNP VRF and Path Isolation Practice Question
This 350-401 practice question tests your understanding of vrf and path isolation. 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.
An enterprise uses VRF-lite on a Cisco Catalyst 9300 to isolate a guest network (VRF GUEST) from the corporate network (VRF CORP). The guest network uses DHCP from a server in the corporate network. The engineer configures a DHCP relay on the guest SVI pointing to the corporate DHCP server. The DHCP server is in VRF CORP. The guest clients are not receiving IP addresses. What is 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
The DHCP server is in a different VRF, and the switch does not have a route from the GUEST VRF to the CORP VRF for the DHCP server.
The DHCP server resides in VRF CORP, but the DHCP relay agent on the guest SVI forwards the discover packet within VRF GUEST. Without a route from VRF GUEST to the DHCP server's subnet in VRF CORP, the relayed packet cannot reach the server. Inter-VRF routing (e.g., a route leak or VRF-aware service) is required for the relay to forward the packet across VRFs.
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.
- ✗
The DHCP relay agent is not configured to use the VRF GUEST; the ip helper-address command must be applied under the VRF interface, but the DHCP server is in a different VRF, requiring inter-VRF routing or the use of the ip dhcp relay information option.
Why it's wrong here
Incorrect because the helper-address is applied on the interface in the GUEST VRF; the issue is that the relay cannot forward to a server in a different VRF without route leaking.
- ✓
The DHCP server is in a different VRF, and the switch does not have a route from the GUEST VRF to the CORP VRF for the DHCP server.
Why this is correct
Correct because DHCP relay forwards the request based on the routing table of the source VRF. Without a route to the server in the GUEST VRF, the relay fails.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The DHCP server is not configured with a scope for the guest subnet.
Why it's wrong here
Incorrect because this would cause the server to not respond, but the relay might still forward the request; the issue is that the request never reaches the server.
- ✗
The guest VRF is missing the ip dhcp relay command globally.
Why it's wrong here
Incorrect because DHCP relay is enabled by default; the global command is not required.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that configuring ip helper-address alone is sufficient for DHCP relay across VRFs, ignoring the need for inter-VRF reachability or route leaking.
Trap categories for this question
Command / output trap
Incorrect because DHCP relay is enabled by default; the global command is not required.
Detailed technical explanation
How to think about this question
In VRF-lite, each VRF maintains its own routing table. When a DHCP relay agent forwards a broadcast as a unicast, it uses the source VRF's routing table to determine the next hop. Without a route in VRF GUEST pointing to the DHCP server's IP (which belongs to VRF CORP), the packet is dropped. This can be resolved by importing/exporting routes between VRFs (e.g., using route-target import/export or a VRF-aware DHCP relay configuration like ip dhcp relay source-interface).
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 network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
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.
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VRF and Path Isolation — study guide chapter
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FAQ
Questions learners often ask
What does this 350-401 question test?
VRF and Path Isolation — This question tests VRF and Path Isolation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The DHCP server is in a different VRF, and the switch does not have a route from the GUEST VRF to the CORP VRF for the DHCP server. — The DHCP server resides in VRF CORP, but the DHCP relay agent on the guest SVI forwards the discover packet within VRF GUEST. Without a route from VRF GUEST to the DHCP server's subnet in VRF CORP, the relayed packet cannot reach the server. Inter-VRF routing (e.g., a route leak or VRF-aware service) is required for the relay to forward the packet across VRFs.
What should I do if I get this 350-401 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
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Last reviewed: Jun 24, 2026
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.
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