The correct design change is to create trunk links with 802.1Q subinterfaces on each switch and assign each subinterface to the appropriate VRF. This works because VRF-Lite operates at Layer 3, and without trunk subinterfaces, each switch maintains isolated VRF routing tables locally but has no way to forward traffic between switches for the same VRF. By deploying 802.1Q trunk subinterfaces, you effectively extend the VRF boundary across the link, allowing the switch to route inter-switch traffic using the correct VRF-specific routing table while keeping tenant traffic fully isolated. On the ENCOR 350-401 exam, this concept tests your understanding of how VRF-Lite differs from MPLS VPNs—VRF-Lite relies entirely on trunk subinterfaces for inter-switch communication, not on MP-BGP or label switching. A common trap is thinking a simple access port or a routed port on a VLAN interface will work, but those cannot carry multiple VRF contexts. Memory tip: think of each subinterface as a separate "virtual router" riding the same physical cable.
CCNP Virtualization Practice Question
This 350-401 practice question tests your understanding of virtualization. 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 connectivity issues in a multi-tenant environment where each tenant's traffic is isolated using VRF-Lite. The engineer notices that tenants in the same VRF cannot communicate with each other across different access switches. Which design change should be implemented to enable inter-switch VRF communication?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create trunk links with 802.1Q subinterfaces on each switch and assign each subinterface to the appropriate VRF.
Option B is correct because VRF-Lite requires 802.1Q trunking to extend Layer 3 VRF boundaries across switches. By creating subinterfaces on trunk links and assigning each subinterface to the appropriate VRF, traffic from the same VRF on different switches can be routed through the VRF-specific routing table, enabling inter-switch communication while maintaining isolation.
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.
✗
Use the same VLAN for all tenants and rely on VLAN ACLs.
Why it's wrong here
VLAN ACLs do not provide routing isolation between VRFs.
✓
Create trunk links with 802.1Q subinterfaces on each switch and assign each subinterface to the appropriate VRF.
Why this is correct
This allows per-VRF routing across switches.
Related concept
Read the scenario before looking for a memorised answer.
✗
Configure static routes on each switch pointing to the next-hop IP in the global routing table.
Why it's wrong here
Static routes in the global table do not provide VRF awareness.
✗
Enable OSPF with a single area on all switches and redistribute between VRFs.
Why it's wrong here
OSPF cannot differentiate VRFs without VRF-aware routing protocols.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that VRF-Lite can use the global routing table for inter-switch communication, but the trap here is that VRF-Lite requires explicit Layer 3 subinterfaces on trunk links to extend VRF boundaries, not just VLANs or static routes in the global table.
Detailed technical explanation
How to think about this question
VRF-Lite uses separate routing tables per tenant, and inter-switch connectivity requires trunk links with 802.1Q subinterfaces (e.g., interface GigabitEthernet0/1.100) each bound to a VRF via the 'ip vrf forwarding' command. The subinterface VLAN tag must match the VLAN used for that VRF on the trunk, and the IP address is assigned within the VRF context, allowing the switch to route traffic between access switches using the correct VRF table. In real-world deployments, this design is common in data center leaf-spine architectures where each tenant's VRF is extended across multiple ToR switches.
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 at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
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.
Virtualization — This question tests Virtualization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create trunk links with 802.1Q subinterfaces on each switch and assign each subinterface to the appropriate VRF. — Option B is correct because VRF-Lite requires 802.1Q trunking to extend Layer 3 VRF boundaries across switches. By creating subinterfaces on trunk links and assigning each subinterface to the appropriate VRF, traffic from the same VRF on different switches can be routed through the VRF-specific routing table, enabling inter-switch communication while maintaining isolation.
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.
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