The answer is that auto-summary is disabled by default for BGP on Cisco IOS-XE routers. This default behavior means that BGP will not automatically summarize subnets to their classful boundaries, such as converting a /24 into a Class A, B, or C network prefix. In the context of MPLS and the Cisco CCNP ENARSI 300-410 exam, this is a critical distinction because many candidates mistakenly assume auto-summary is enabled, as it is for certain older routing protocols like RIP version 1. The exam tests your understanding that BGP, unlike those protocols, treats all prefixes as exact and will not perform classful summarization unless explicitly configured with the auto-summary command. A common trap is confusing BGP’s behavior with EIGRP or RIP, where auto-summary may be on by default in older IOS versions. To remember: think “BGP is classless by nature—no automatic classful summarization.”
300-410 MPLS Operations Practice Question
This 300-410 practice question tests your understanding of mpls operations. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
In MPLS, what is the default behavior of a Cisco IOS-XE router regarding the 'auto-summary' command for BGP routes?
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 for BGP.
By default, auto-summary is disabled in Cisco IOS-XE for BGP, meaning that BGP will not automatically summarize subnets to their classful boundaries.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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 disabled by default for BGP.
Why this is correct
Cisco IOS-XE disables auto-summary by default for BGP since version 12.2(8)T.
Auto-summary is enabled by default for EIGRP and RIP, but not for BGP in modern IOS-XE.
✗
Auto-summary is enabled by default only for directly connected routes.
Why it's wrong here
Auto-summary applies to routes learned via the protocol, not just directly connected.
✗
Auto-summary is disabled by default for BGP but enabled for OSPF.
Why it's wrong here
OSPF does not use auto-summary; it uses area summarization.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
OSPF neighbours must agree on key parameters.
Router ID selection can affect neighbour relationships and LSDB output.
OSPF cost influences the preferred path.
A route can appear in OSPF information but not become the installed route.
TExam Day Tips
→Check area mismatch first when OSPF adjacency fails.
→Review passive interfaces when a network is advertised but no neighbour forms.
→Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
MPLS Operations — This question tests MPLS Operations — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: Auto-summary is disabled by default for BGP. — By default, auto-summary is disabled in Cisco IOS-XE for BGP, meaning that BGP will not automatically summarize subnets to their classful boundaries.
What should I do if I get this 300-410 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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Question Discussion
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