hardMultiple Choice
300-410 Practice Question: Which statement about the default behavior of…
Which statement about the default behavior of 'auto-summary' in EIGRP for DMVPN tunnel interfaces in IOS-XE is correct?
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, preventing classful summarization.
In modern IOS-XE versions (15.x and later), auto-summary is disabled by default for EIGRP. This is a change from older IOS versions where it was enabled by default. Disabling auto-summary is essential in DMVPN to prevent incorrect summarization at classful boundaries.
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 and summarizes routes at classful boundaries.
Why it's wrong here
IOS-XE disables EIGRP auto-summary by default, so it neither runs nor summarises at classful boundaries unless configured. The classful-summarisation description is tempting because auto-summary did behave that way on older IOS releases, and would be correct there rather than on current DMVPN tunnel interfaces.
- ✓
Auto-summary is disabled by default, preventing classful summarization.
Why this is correct
Auto-summary is disabled by default on EIGRP, so classful summarisation at major network boundaries does not occur. This satisfies the DMVPN requirement for carrying discontiguous or overlapping tunnel subnets, since spoke and hub prefixes are advertised precisely rather than collapsed into a classful summary that would blackhole traffic.
- ✗
Auto-summary is enabled by default but only for tunnel interfaces.
Why it's wrong here
Auto-summary is disabled by default in IOS-XE EIGRP, and the feature is interface-independent, never scoped to tunnels alone. Restricting it to tunnel interfaces is tempting because DMVPN designs often tune summarisation there, and would be correct if the stem asked about manual summary-address configuration on tunnel interfaces.
- ✗
Auto-summary is disabled by default but can be enabled only for DMVPN.
Why it's wrong here
EIGRP auto-summary is disabled by default on IOS-XE and can be enabled on any interface, not restricted to DMVPN tunnels. It is tempting because DMVPN designs often discuss summarisation at the hub, but that concerns manual interface summary configuration, not a DMVPN-only auto-summary capability.
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.