The answer is that R1 is not an ABR, so the area 0 range command does not generate a summary route. The OSPF route summarization feature only works on an ABR (connecting area 0 to a non-zero area) or an ASBR, and since R1 has all interfaces in area 0, it has no inter-area routes to summarize. The network type mismatch between R1’s point-to-point and R2’s broadcast does cause DR/BDR election issues and can disrupt LSA flooding, but the neighbor state shows FULL, meaning the adjacency is technically up—the real root cause is the missing ABR role. On the Cisco CCNP ENARSI 300-410 exam, this question tests your understanding that the area range command is not a magic bullet; it only takes effect when the router is summarizing routes between areas. A common trap is to blame the network type mismatch or assume the summary is automatically generated, but the key insight is that a single-area OSPF configuration cannot produce inter-area summaries. Memory tip: “No ABR, no area range—summaries need a border to exchange.”
300-410 Route Summarization Practice Question
This 300-410 practice question tests your understanding of route summarization. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
OSPF network type mismatch on a multi-access link is causing route summarization issues. Router R1 and R2 are connected via Ethernet, but R1 has:
interface GigabitEthernet0/0
ip address 10.0.0.1 255.255.255.0
ip ospf network point-to-point
ip ospf 1 area 0
!
Router R2 has default OSPF network type (broadcast). R1 is configured with:
router ospf 1
area 0 range 10.0.0.0 255.255.255.0
!
R2 shows:
R2# show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
10.0.0.1 0 FULL/ - 00:00:30 10.0.0.1 GigabitEthernet0/0
But R2 does not have the summary route in its routing table. What is the root cause?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
R1 is not an ABR (only area 0), so the area range command does not generate a summary route.
The network type mismatch (point-to-point on R1, broadcast on R2) prevents proper adjacency formation. Although the neighbor state shows FULL, the DR/BDR election is affected. R1's point-to-point setting means it does not participate in DR election, and R2 expects a DR. This can cause LSA flooding issues, and the area range summary may not be advertised correctly. The summary route is generated by the ABR, but if R1 is not an ABR (area 0 only), the range command has no effect. The root cause is that R1 is not an ABR, so area range does not apply.
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.
✓
R1 is not an ABR (only area 0), so the area range command does not generate a summary route.
Why this is correct
Area range only works on ABRs that connect multiple areas.
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.
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 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.
Route Summarization — This question tests Route Summarization — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: R1 is not an ABR (only area 0), so the area range command does not generate a summary route. — The network type mismatch (point-to-point on R1, broadcast on R2) prevents proper adjacency formation. Although the neighbor state shows FULL, the DR/BDR election is affected. R1's point-to-point setting means it does not participate in DR election, and R2 expects a DR. This can cause LSA flooding issues, and the area range summary may not be advertised correctly. The summary route is generated by the ABR, but if R1 is not an ABR (area 0 only), the range command has no effect. The root cause is that R1 is not an ABR, so area range does not apply.
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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