mediumMultiple Choice
300-410 Practice Question: Which statement accurately describes the default…
Which statement accurately describes the default behavior of auto-summary in EIGRP on Cisco IOS-XE?
⚠ Common exam trap
Cisco often tests the misconception that auto-summary is still enabled by default in EIGRP on modern IOS-XE, when in fact it was changed to disabled by default starting from IOS 15.0(1)M and later.
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
✓
Auto-summary is disabled by default, and EIGRP advertises subnets without automatic summarization.
In Cisco IOS-XE, EIGRP auto-summary is disabled by default. This means that EIGRP advertises subnets without automatically summarizing them at classful boundaries, allowing for more granular route advertisement and preventing routing issues in discontiguous networks.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Auto-summary is enabled by default, causing EIGRP to summarize at classful boundaries.
Why it's wrong here
On Cisco IOS-XE, EIGRP auto-summary is disabled by default; summarisation at classful boundaries must be enabled manually with 'auto-summary'. It would be the correct behaviour on much older IOS releases, which is why the classful-boundary description is tempting, but IOS-XE defaults to no auto-summary.
- ✓
Auto-summary is disabled by default, and EIGRP advertises subnets without automatic summarization.
Why this is correct
Cisco IOS-XE ships with EIGRP auto-summary disabled, so classful boundary summarisation never occurs unless explicitly enabled with the auto-summary command. Subnets are therefore advertised individually with their configured masks, matching the stem's requirement for accurate default behaviour.
- ✗
Auto-summary is enabled by default but only for external routes.
Why it's wrong here
Auto-summary on IOS-XE is disabled by default for all EIGRP routes, internal and external alike; there is no external-only default. The option invents a scope restriction that does not exist. Enabling it applies classful summarisation generally, which is why the external-route qualifier misleads.
- ✗
Auto-summary is disabled by default unless the network is configured with a classful mask.
Why it's wrong here
Auto-summary is disabled by default in EIGRP regardless of mask configuration, so the conditional clause misstates IOS-XE behaviour. It tempts because classful boundaries genuinely govern summarisation when auto-summary is enabled, making classful masks seem relevant. Auto-summary would be the correct focus only if the question asked about legacy IOS versions where it defaulted to enabled.
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.
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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.