hardMultiple ChoiceObjective-mapped
300-410 Practice Question: A service provider network uses OSPF with route…
A service provider network uses OSPF with route summarization on Area Border Routers (ABRs). Router R1 (ABR) has the configuration:
router ospf 1
area 1 range 10.1.0.0 255.255.240.0
area 1 range 10.1.16.0 255.255.240.0
Router R2 (internal to area 1) shows:
R2# show ip route ospf
10.1.0.0/20 is subnetted, 1 subnetsO IA 10.1.0.0/20 [110/2] via 10.2.1.1, 00:00:15, Serial0/0/0
10.1.16.0/20 is subnetted, 1 subnets
O IA 10.1.16.0/20 [110/2] via 10.2.1.1, 00:00:10, Serial0/0/0
10.1.32.0/20 [110/3] via 10.2.1.2, 00:00:05, Serial0/0/1
R2 is missing a route to 10.1.48.0/20. 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 ABR R1 has a missing 'area 1 range 10.1.48.0 255.255.240.0' command.
The ABR R1 configured two summary ranges for area 1, but the missing route 10.1.48.0/20 is not covered by either summary. OSPF summarization on the ABR creates Type 3 LSAs for the configured ranges, but any routes not falling within those ranges are not advertised as summaries and are also not advertised as individual routes (unless the 'no discard-route' option is used). This causes the missing route. The correct fix is to add an additional summary range covering 10.1.48.0/20 or use a broader summary.
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 ABR R1 has a missing 'area 1 range 10.1.48.0 255.255.240.0' command.
Why this is correct
The summary range for 10.1.48.0/20 is not configured, so that route is not advertised into area 0.
- ✗
R2 has a routing table limit that prevents installation of the route.
Why it's wrong here
There is no indication of a routing table limit; R2 receives other routes.
- ✗
R1's OSPF process has a distribute-list blocking the route.
Why it's wrong here
No distribute-list is shown in the configuration.
- ✗
The missing route is a result of OSPF route filtering at the area boundary.
Why it's wrong here
Route filtering is not configured; the issue is incomplete summarization.
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
Introduction to ENARSI Exam and Network Fundamentals
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.
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.
About these practice questions
This 300-410 question is part of Courseiva's 1,966-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 →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.