hardMultiple Choice
OSPF Route Summarization: Troubleshooting ABR and Network Type Issues
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?
Quick Answer
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.”
⚠ Common exam trap
The trap here is assuming that any router can perform area summarization with the area range command, when in fact only ABRs can generate inter-area summary routes; candidates may be distracted by the network type mismatch and incorrectly attribute the missing summary to that.
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
✓
R1 is not an ABR (only area 0), so the area range command does not generate a summary route.
The area range command is used on an Area Border Router (ABR) to summarize Type-3 LSAs between areas. R1 is only in area 0 (backbone), so it is not an ABR and cannot generate inter-area summary routes. Therefore, the area range command has no effect, and R2 will not receive a summary route. The network type mismatch does not prevent LSA exchange because the neighbor relationship is FULL, as shown in the output.
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
The area range command only generates a summary LSA when the router is an ABR with interfaces in multiple areas. R1 has only area 0, so it is an internal router and cannot originate a type-3 summary into another area.
- ✗
The network type mismatch causes OSPF to not exchange LSAs correctly, preventing the summary.
Why it's wrong here
OSPF still forms FULL adjacency and exchanges LSAs across a network-type mismatch; the LSDB synchronises normally. The real fault is that R1's point-to-point interface is advertised as a stub network, so the area range has no matching intra-area routes to summarise. Mismatched types are tolerated in many designs.
- ✗
The summary route is suppressed because the interface is point-to-point.
Why it's wrong here
Point-to-point interfaces still flood Type 3 summary LSAs, so suppression is not the mechanism. The mismatch itself is the issue: R1's point-to-point link is treated as a stub network, so no Type 2 LSA exists and the summary is not generated as expected. Point-to-point is correct on true serial links.
- ✗
R2 has a static route that overrides the summary.
Why it's wrong here
A static route would appear in the routing table and be preferred over OSPF, but R2 shows no summary route at all, so none exists to override. It is tempting because administrative distance genuinely explains why a static route would win over an OSPF summary.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
Go deeper
Related to this question
Learn chapter
OSPF Neighbor Adjacency and Basics
Key term
BGP Route Aggregation
BGP Route Aggregation is a technique that combines multiple specific network routes into a single summary route to reduce the size of routing tables and improve network efficiency.
Key term
OSPF Route Summarization
OSPF route summarization is a technique that combines multiple smaller network routes into a single, larger route advertisement to reduce the size of routing tables and improve network stability.
About these practice questions
This 300-410 question is part of Courseiva's 1,401-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more way this is tested on 300-410
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which OSPF LSA type is used to advertise a summary route for a network outside the area but within the same OSPF domain?
medium- A.Type 1
- B.Type 2
- ✓ C.Type 3
- D.Type 5
Why C: OSPF Type 3 LSAs (Summary LSAs) are generated by Area Border Routers (ABRs) to advertise networks from one area into another area within the same OSPF domain. They describe inter-area routes, which are routes to networks outside the local area but still within the OSPF autonomous system. Therefore, a summary route for a network outside the area but within the same OSPF domain is advertised via Type 3 LSA.
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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.