The answer is that the host’s IP address is not in the same subnet as the router’s interface IP in VRF_GREEN. This is the most likely cause because when a ping fails in VRF-Lite despite the interface being up/up and the connected route for the host’s subnet appearing in the VRF routing table, the router cannot perform ARP resolution for a gateway IP that lies outside its own directly connected subnet. In VRF-Lite, each VRF maintains its own separate routing and forwarding tables, so the router will only attempt to resolve the next-hop IP if it falls within the same subnet as the interface’s configured IP; otherwise, the packet is dropped. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of VRF-Lite’s Layer 2 adjacency requirements—a common trap is assuming a valid route guarantees reachability, when in fact the host’s gateway must match the router’s interface subnet exactly. A helpful memory tip: “Route is there, but ARP won’t care if the subnet’s not a pair.”
300-410 VRF-Lite Practice Question
This 300-410 practice question tests your understanding of vrf-lite. 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 engineer is troubleshooting a VRF-Lite setup where a router is configured with VRF_GREEN. The engineer pings the gateway IP of a host in VRF_GREEN from the router, but the ping fails. The 'show ip route vrf VRF_GREEN' command shows the connected network for the host's subnet. The 'show ip interface brief' shows the interface is up/up. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
The host's default gateway is not set to the router's interface IP in VRF_GREEN.
Why wrong: This would cause the host to not send traffic to the router, but the router's ping to the host should still work if the host responds to ARP.
B
The router's interface in VRF_GREEN has 'ip proxy-arp' disabled.
Why wrong: Proxy ARP is not needed for direct communication within the same subnet.
C
The host's IP address is not in the same subnet as the router's interface IP in VRF_GREEN.
If the host's IP is in a different subnet, the router will not have a connected route for that host, and ARP will fail.
D
The 'ip routing' command is disabled in VRF_GREEN.
Why wrong: IP routing is a global command and cannot be disabled per VRF.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The host's IP address is not in the same subnet as the router's interface IP in VRF_GREEN.
If the interface is up and the route is present, the issue might be with ARP resolution or the host's configuration. However, in VRF-Lite, the router might not be able to ping the gateway if the gateway IP is not in the same subnet as the interface IP, or if the host has a firewall blocking ICMP.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 host's default gateway is not set to the router's interface IP in VRF_GREEN.
Why it's wrong here
This would cause the host to not send traffic to the router, but the router's ping to the host should still work if the host responds to ARP.
✗
The router's interface in VRF_GREEN has 'ip proxy-arp' disabled.
Why it's wrong here
Proxy ARP is not needed for direct communication within the same subnet.
✓
The host's IP address is not in the same subnet as the router's interface IP in VRF_GREEN.
Why this is correct
If the host's IP is in a different subnet, the router will not have a connected route for that host, and ARP will fail.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
The 'ip routing' command is disabled in VRF_GREEN.
Why it's wrong here
IP routing is a global command and cannot be disabled per VRF.
Common exam traps
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.
Trap categories for this question
Command / output trap
IP routing is a global command and cannot be disabled per VRF.
Detailed technical explanation
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.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 300-410 subnetting questions on CIDR, address ranges, and subnet selection.
VRF-Lite — This question tests VRF-Lite — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The host's IP address is not in the same subnet as the router's interface IP in VRF_GREEN. — If the interface is up and the route is present, the issue might be with ARP resolution or the host's configuration. However, in VRF-Lite, the router might not be able to ping the gateway if the gateway IP is not in the same subnet as the interface IP, or if the host has a firewall blocking ICMP.
What should I do if I get this 300-410 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 300-410 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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 →
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.
This 300-410 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 300-410 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.