Question 387 of 500
ArchitecturemediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is that a higher local preference is the attribute causing the router to prefer the route with the longer AS path. In BGP path selection, local preference is evaluated before AS path length, meaning a route with a higher local preference is always chosen, regardless of how many AS prepends have been added. This is a critical concept for the Cisco SPCOR / CCNP Service Provider Core 350-501 exam, where questions often test your understanding of the BGP best-path algorithm order. A common trap is assuming a shorter AS path always wins, but local preference overrides it entirely. Remember the mnemonic: "We Love Oranges AS Oranges" — Weight, Local Preference, Originate, AS path, Origin, MED, and so on — to keep the evaluation order straight.

350-501 Architecture Practice Question

This 350-501 practice question tests your understanding of architecture. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.

A service provider is troubleshooting BGP route selection for prefixes received from two different peers. The first peer prepends its AS path twice, making it longer than the second peer's path. However, the router still prefers the route with the longer AS path. Which additional attribute could cause this behavior?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

  • Clue: "first"

    Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.

Question 1mediummultiple choice
Open the full BGP breakdown →

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

The route has a higher local preference

In BGP, the path with higher local preference is preferred regardless of AS path length. If both have same local preference, then shortest AS path wins. Here, the longer AS path is preferred, meaning the local preference must be higher on that route. Weight is Cisco-proprietary and local to the router; if set, it can override local preference. MED is compared only if paths come from the same AS. Origin type is compared after AS path. Community affects but does not directly override AS path length.

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.

  • The route has a lower MED

    Why it's wrong here

    MED influences only when paths are from the same AS; it does not override AS path length.

  • The route has a higher weight

    Why it's wrong here

    Weight is considered before local preference, but if both routes have default weight (0), local preference decides. However, if one has higher weight, it would be preferred, but that would also override local preference; but typically weight is not set in this scenario. Nonetheless, local preference is the more common cause.

  • The route has a lower origin type

    Why it's wrong here

    Origin is considered after AS path length; it cannot override a longer AS path.

  • The route has a higher local preference

    Why this is correct

    Local preference is the first criterion in BGP path selection; a higher value will be chosen regardless of AS path length.

    Clue confirmation

    The clue word "first" in the question point toward this answer.

    Related concept

    OSPF neighbours must agree on key parameters.

  • The route has a lower neighbor router ID

    Why it's wrong here

    Router ID is a tiebreaker after all other attributes; it does not override AS path length.

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.

Trap categories for this question

  • Scenario analysis trap

    Weight is considered before local preference, but if both routes have default weight (0), local preference decides. However, if one has higher weight, it would be preferred, but that would also override local preference; but typically weight is not set in this scenario. Nonetheless, local preference is the more common cause.

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.

What to study next

Got this wrong? Here's your next step.

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 350-501 OSPF questions on adjacency and route selection.

Related practice questions

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FAQ

Questions learners often ask

What does this 350-501 question test?

Architecture — This question tests Architecture — OSPF neighbours must agree on key parameters..

What is the correct answer to this question?

The correct answer is: The route has a higher local preference — In BGP, the path with higher local preference is preferred regardless of AS path length. If both have same local preference, then shortest AS path wins. Here, the longer AS path is preferred, meaning the local preference must be higher on that route. Weight is Cisco-proprietary and local to the router; if set, it can override local preference. MED is compared only if paths come from the same AS. Origin type is compared after AS path. Community affects but does not directly override AS path length.

What should I do if I get this 350-501 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 350-501 OSPF questions on adjacency and route selection.

Are there clue words in this question I should notice?

Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.

What is the key concept behind this question?

OSPF neighbours must agree on key parameters.

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Last reviewed: Jun 24, 2026

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