- A
The route-target export on R1 (100:1) does not match the route-target import on R2 (100:2), so R2 does not import routes from R1.
VRF-lite relies on route-target matching for route import/export. Since the RTs differ, R2 does not import any routes from R1, even though OSPF is running in the VRF. OSPF only propagates routes within the same VRF, not between VRFs.
- B
The OSPF process on R1 is not configured with the 'vrf BLUE' keyword.
Why wrong: If OSPF were not in the VRF, the route would not appear in the VRF table at all.
- C
The link between R1 and R2 is not in the VRF, so OSPF cannot form adjacency.
Why wrong: The link is in the global routing table, but OSPF in the VRF can use a different interface; the adjacency must be over an interface in the VRF.
- D
The route 10.1.1.0/24 is being filtered by a distribute-list in OSPF.
Why wrong: There is no indication of filtering; the issue is RT mismatch.
Quick Answer
The answer is a route-target mismatch between R1 and R2, because the route-target export 100:1 on R1 does not match the route-target import 100:2 on R2, preventing R2 from importing the OSPF-learned route. In VRF-lite, route leaking between VRFs is not automatic; even when OSPF is running within a VRF, it only propagates routes within that same VRF instance. For a route to be shared across different VRFs, the export RT on the source VRF must exactly match the import RT on the destination VRF—here, 100:1 versus 100:2 breaks that link. This scenario directly tests your understanding of VRF-lite route leaking on the Cisco CCNP ENARSI 300-410 exam, where a common trap is assuming OSPF alone will leak routes between VRFs. Remember: OSPF handles intra-VRF routing, but RT values control inter-VRF import/export. Memory tip: "RTs must match to catch the leak"—if the export and import tags don't align, the route stays stuck.
300-410 Route Maps and Route Filtering Practice Question
This 300-410 practice question tests your understanding of route maps and route filtering. 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 reachability issues in a VRF-lite environment. R1 has the following configuration: ip vrf BLUE rd 100:1 route-target export 100:1 route-target import 100:1. R2 has: ip vrf BLUE rd 100:2 route-target export 100:2 route-target import 100:2. Both routers are connected via a link in the global routing table and are running OSPF in the VRF. R1 shows: 'show ip route vrf BLUE' has a route to 10.1.1.0/24 via OSPF, but R2 shows: 'show ip route vrf BLUE' does not have this route. What is the root cause?
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 route-target export on R1 (100:1) does not match the route-target import on R2 (100:2), so R2 does not import routes from R1.
In VRF-lite, route leaking between VRFs is not automatic; it requires explicit configuration using route-map or VRF import/export policies. The RT values on R1 and R2 are different (100:1 vs 100:2), so even if OSPF is running within the VRF, routes are not shared because the route-target import/export do not match. OSPF in a VRF only propagates routes within the same VRF; it does not automatically leak routes to other VRFs. The correct configuration would be to either use the same RT on both routers or configure a route-map to leak routes.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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 route-target export on R1 (100:1) does not match the route-target import on R2 (100:2), so R2 does not import routes from R1.
Why this is correct
VRF-lite relies on route-target matching for route import/export. Since the RTs differ, R2 does not import any routes from R1, even though OSPF is running in the VRF. OSPF only propagates routes within the same VRF, not between VRFs.
Related concept
OSPF neighbours must agree on key parameters.
- ✗
The OSPF process on R1 is not configured with the 'vrf BLUE' keyword.
Why it's wrong here
If OSPF were not in the VRF, the route would not appear in the VRF table at all.
- ✗
The link between R1 and R2 is not in the VRF, so OSPF cannot form adjacency.
Why it's wrong here
The link is in the global routing table, but OSPF in the VRF can use a different interface; the adjacency must be over an interface in the VRF.
- ✗
The route 10.1.1.0/24 is being filtered by a distribute-list in OSPF.
Why it's wrong here
There is no indication of filtering; the issue is RT mismatch.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
- OSPF neighbours must agree on key parameters.
- Router ID selection can affect neighbour relationships and LSDB output.
- OSPF cost influences the preferred path.
- A route can appear in OSPF information but not become the installed route.
TExam Day Tips
- Check area mismatch first when OSPF adjacency fails.
- Review passive interfaces when a network is advertised but no neighbour forms.
- Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
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FAQ
Questions learners often ask
What does this 300-410 question test?
Route Maps and Route Filtering — This question tests Route Maps and Route Filtering — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The route-target export on R1 (100:1) does not match the route-target import on R2 (100:2), so R2 does not import routes from R1. — In VRF-lite, route leaking between VRFs is not automatic; it requires explicit configuration using route-map or VRF import/export policies. The RT values on R1 and R2 are different (100:1 vs 100:2), so even if OSPF is running within the VRF, routes are not shared because the route-target import/export do not match. OSPF in a VRF only propagates routes within the same VRF; it does not automatically leak routes to other VRFs. The correct configuration would be to either use the same RT on both routers or configure a route-map to leak routes.
What should I do if I get this 300-410 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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Last reviewed: Jun 18, 2026
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