- A
The BGP synchronization rule is enabled, and the IGP does not have a route for the prefix, so BGP does not advertise the route.
Why wrong: Synchronization affects BGP advertisement, not installation of received routes. The route is already in the BGP table.
- B
The next-hop of the iBGP route is not reachable via any route in the VRF routing table, so the route is not installed.
iBGP requires the next-hop to be reachable. If the next-hop (e.g., a loopback) is not in the IGP, the route is not installed.
- C
The 'maximum-paths' command is set to 1, and there is already a route with a lower administrative distance.
Why wrong: Maximum-paths affects load balancing, not installation. If the route is not installed, it is not due to path count.
- D
The BGP table shows the route as 'rR' (rIBGP and RIB-failure), indicating a RIB failure due to a higher metric.
Why wrong: RIB-failure is due to administrative distance or route type, not next-hop unreachability. Next-hop unreachability shows as 'r' (not installed).
Quick Answer
The answer is that the iBGP routes are not installed because the next-hop is unreachable within the VRF routing table. In iBGP, by default, a route is only eligible for installation if its next-hop address is reachable via an IGP or static route in the same VRF; if the VRF’s OSPF process does not advertise the loopback or interface used as the next-hop, BGP considers the route hidden and refuses to place it in the routing table. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of VRF-Lite’s separation of routing tables and the critical rule that iBGP does not recursively resolve next-hops across VRFs—a common trap is confusing this with BGP synchronization or missing the `bgp redistribute-internal` command. Remember the key: for iBGP in a VRF, the next-hop must be an IGP-known address within that same VRF, or the route stays hidden. Memory tip: “No IGP hop, no BGP drop.”
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 configures iBGP within a VRF-Lite environment. The VRF has an IGP (OSPF) running, and BGP is used to exchange customer routes. The engineer notices that BGP routes are not being installed in the VRF routing table, even though they are present in the BGP table. The 'bgp redistribute-internal' command is not configured. Which is the most likely explanation?
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.
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 next-hop of the iBGP route is not reachable via any route in the VRF routing table, so the route is not installed.
In iBGP, the next-hop for a route learned from an iBGP peer must be reachable via an IGP or static route. If the next-hop is not reachable, the route is not installed in the routing table. Additionally, if the IGP does not carry the next-hop route (e.g., because it is a loopback not advertised), the route remains hidden. This is a common edge case where synchronization is not the issue, but next-hop reachability is.
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 BGP synchronization rule is enabled, and the IGP does not have a route for the prefix, so BGP does not advertise the route.
Why it's wrong here
Synchronization affects BGP advertisement, not installation of received routes. The route is already in the BGP table.
- ✓
The next-hop of the iBGP route is not reachable via any route in the VRF routing table, so the route is not installed.
- ✗
The 'maximum-paths' command is set to 1, and there is already a route with a lower administrative distance.
Why it's wrong here
Maximum-paths affects load balancing, not installation. If the route is not installed, it is not due to path count.
- ✗
The BGP table shows the route as 'rR' (rIBGP and RIB-failure), indicating a RIB failure due to a higher metric.
Why it's wrong here
RIB-failure is due to administrative distance or route type, not next-hop unreachability. Next-hop unreachability shows as 'r' (not installed).
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.
Trap categories for this question
Command / output trap
RIB-failure is due to administrative distance or route type, not next-hop unreachability. Next-hop unreachability shows as 'r' (not installed).
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?
VRF-Lite — This question tests VRF-Lite — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The next-hop of the iBGP route is not reachable via any route in the VRF routing table, so the route is not installed. — In iBGP, the next-hop for a route learned from an iBGP peer must be reachable via an IGP or static route. If the next-hop is not reachable, the route is not installed in the routing table. Additionally, if the IGP does not carry the next-hop route (e.g., because it is a loopback not advertised), the route remains hidden. This is a common edge case where synchronization is not the issue, but next-hop reachability is.
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.
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?
OSPF neighbours must agree on key parameters.
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Last reviewed: Jun 18, 2026
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