- A
A summary route is advertised with the metric equal to the best metric among the component routes.
Correct. EIGRP uses the best (lowest) metric from the component routes for the summary route advertisement.
- B
The summary route is automatically assigned an administrative distance of 90 by default.
Why wrong: Incorrect. The default administrative distance for an EIGRP summary route is 5, not 90. The AD of 90 is for internal EIGRP routes.
- C
A local discard route (null0) is automatically installed for the summary prefix to prevent routing loops.
Correct. EIGRP automatically installs a discard route (to Null0) for the summary prefix to avoid loops when the more specific routes are not present.
- D
The 'summary-address' command also summarizes connected routes that fall within the summary range.
Why wrong: Incorrect. Connected routes are not automatically summarized; they must be redistributed into EIGRP first.
- E
More specific routes are still advertised out the same interface even after the summary is configured.
Why wrong: Incorrect. The purpose of the summary-address command is to suppress the advertisement of more specific routes out that interface.
Quick Answer
The correct answer is that a local discard route (null0) is automatically installed for the summary prefix to prevent routing loops. This occurs because EIGRP’s summary-address command, when configured under an interface, creates a summary route that aggregates more specific routes; the null0 route ensures that if a packet matches the summary but not a more specific entry, it is dropped rather than potentially looping back through the network. On the Cisco CCNP ENARSI 300-410 exam, this behavior tests your understanding of how EIGRP prevents black holes and routing loops during summarization—a common trap is thinking the summary route inherits the administrative distance of 90 like a regular EIGRP route, but it actually defaults to 5. Remember the memory tip: “Summarize with null0, AD 5, not 90” to avoid confusing the discard route’s administrative distance with that of learned routes.
300-410 Route Summarization Practice Question
This 300-410 practice question tests your understanding of route summarization. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
- ✗
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.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Command / output trap
Incorrect. The purpose of the summary-address command is to suppress the advertisement of more specific routes out that interface.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 300-410 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which 300-410 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Questions learners often ask
What does this 300-410 question test?
Route Summarization — This question tests Route Summarization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this 300-410 question wrong?
Identify which 300-410 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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.
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Last reviewed: Jun 18, 2026
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