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300-410 Practice Question: Which TWO statements correctly describe the…
Which TWO statements correctly describe the behavior of EIGRP route summarization when using the 'summary-address' command under an interface? (Choose TWO.)
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
✓
A summary route is advertised with the metric equal to the best metric among the component routes.
EIGRP route summarization using the interface-level 'summary-address' command creates a local discard route to prevent routing loops, suppresses more specific routes from being advertised out that interface, and does not automatically summarize connected routes unless they are redistributed. The summary route is advertised with the metric of the best component route, and the administrative distance of the summary is set to 5 by default, not 90.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
A summary route is advertised with the metric equal to the best metric among the component routes.
Why this is correct
Correct. EIGRP uses the best (lowest) metric from the component routes for the summary route advertisement.
- ✗
The summary route is automatically assigned an administrative distance of 90 by default.
Why it's wrong here
Incorrect. The default administrative distance for an EIGRP summary route is 5, not 90. The AD of 90 is for internal EIGRP routes.
- ✓
A local discard route (null0) is automatically installed for the summary prefix to prevent routing loops.
Why this is correct
Correct. EIGRP automatically installs a discard route (to Null0) for the summary prefix to avoid loops when the more specific routes are not present.
- ✗
The 'summary-address' command also summarizes connected routes that fall within the summary range.
Why it's wrong here
Incorrect. Connected routes are not automatically summarized; they must be redistributed into EIGRP first.
- ✗
More specific routes are still advertised out the same interface even after the summary is configured.
Why it's wrong here
Incorrect. The purpose of the summary-address command is to suppress the advertisement of more specific routes out that interface.
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 Route Summarization and Filtering
Key term
EIGRP Route Summarization
EIGRP route summarization is a technique that combines multiple specific network routes into one summary route to reduce routing table size 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.
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Same concept, more angles
2 more ways 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. In EIGRP, what is the default behavior of auto-summary in IOS-XE versions 15.0 and later?
medium- A.Auto-summary is enabled by default.
- ✓ B.Auto-summary is disabled by default.
- C.Auto-summary is enabled only for EIGRP named mode.
- D.Auto-summary is disabled only for EIGRP classic mode.
Why B: Cisco IOS-XE 15.0 and later have auto-summary disabled by default for EIGRP, unlike older IOS versions where it was enabled by default.
Variation 2. A network engineer is troubleshooting a connectivity issue between two branches connected via a WAN link. Router R1 (10.1.0.0/16) is summarizing its directly connected subnets (10.1.1.0/24, 10.1.2.0/24, 10.1.3.0/24) as a single 10.1.0.0/16 route to Router R2 via EIGRP. Users at R2 report that they cannot reach the 10.1.4.0/24 subnet, which was recently added to R1. What is the most likely cause of the problem?
medium- A.The summary route 10.1.0.0/16 was configured manually, and the new subnet 10.1.4.0/24 is not within the summary range because the mask is too specific.
- ✓ B.The new subnet 10.1.4.0/24 was not advertised because the summary address command suppresses more specific routes, but the summary itself is not being generated due to a missing network statement under the EIGRP process.
- C.The WAN link is down, causing R2 to lose the summary route.
- D.The engineer forgot to configure the summary address on the interface facing R2 for the new subnet.
Why B: The summary route 10.1.0.0/16 includes the new subnet 10.1.4.0/24, but the issue indicates that the summary is not being updated or is too broad, causing a mismatch. The most likely cause is that the summary address was configured manually and does not automatically include new subnets unless the summary range is adjusted.
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.