Question 609 of 2,152

Administrative Distance →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the distance bgp 20 200 200 command has been configured under the BGP process, which overrides the default administrative distance for eBGP routes from 20 to 200. This is correct because the BGP administrative distance command directly modifies the trustworthiness of learned routes; with eBGP’s AD raised to 200, it becomes less preferred than OSPF’s default AD of 110, causing the OSPF route to be installed in the routing table. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of how the distance bgp command can disrupt expected BGP route selection, often appearing as a troubleshooting trap where an engineer assumes default AD values are in effect. A common memory tip is to remember that the distance bgp command takes three arguments—external, internal, and local—so if you see an eBGP route losing to an IGP, check for a modified external distance.

300-410 Administrative Distance Practice Question

This 300-410 practice question tests your understanding of administrative distance. 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 network engineer is troubleshooting a BGP route reachability issue. R1 learns the prefix 10.1.1.0/24 via eBGP from R2 with an AD of 20, and via OSPF from R3 with an AD of 110. The engineer notices that R1 installs the OSPF route in the routing table instead of the eBGP route, even though the eBGP route is preferred by default. What is the most likely cause of this behavior?

Clue words in this question

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

Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

Question 1mediummultiple choice

Review the full OSPF breakdown →

A
The OSPF route has a lower metric than the eBGP route.
Why wrong: Administrative distance is compared before metric; eBGP AD 20 is lower than OSPF AD 110 regardless of metric.
B
The distance bgp 20 200 200 command is configured under the BGP process, increasing the AD of eBGP routes to 200.
This command sets the AD for eBGP routes to 200, making OSPF (AD 110) preferred.
C
The OSPF route is an inter-area route, which has a lower AD than intra-area routes.
Why wrong: OSPF AD is fixed at 110 for all OSPF routes unless modified; inter-area does not change AD.
D
The eBGP route is not the best path because the next-hop is unreachable.
Why wrong: If the next-hop were unreachable, the route would not be installed at all, but the symptom states the OSPF route is installed, not that eBGP is missing.

Full breakdown with real-world context →

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 distance bgp 20 200 200 command is configured under the BGP process, increasing the AD of eBGP routes to 200.

The default administrative distance for eBGP is 20, and for OSPF is 110, so eBGP should be preferred. However, if the distance command is applied to the eBGP neighbor or the BGP process, it can increase the AD of eBGP routes, making them less preferred than OSPF.

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 OSPF route has a lower metric than the eBGP route.
Why it's wrong here
Administrative distance is compared before metric; eBGP AD 20 is lower than OSPF AD 110 regardless of metric.
✓
The distance bgp 20 200 200 command is configured under the BGP process, increasing the AD of eBGP routes to 200.
Why this is correct
This command sets the AD for eBGP routes to 200, making OSPF (AD 110) preferred.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
OSPF neighbours must agree on key parameters.
✗
The OSPF route is an inter-area route, which has a lower AD than intra-area routes.
Why it's wrong here
OSPF AD is fixed at 110 for all OSPF routes unless modified; inter-area does not change AD.
✗
The eBGP route is not the best path because the next-hop is unreachable.
Why it's wrong here
If the next-hop were unreachable, the route would not be installed at all, but the symptom states the OSPF route is installed, not that eBGP is missing.

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.

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 300-410 OSPF questions on adjacency and route selection.

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FAQ

Questions learners often ask

What does this 300-410 question test?

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

What is the correct answer to this question?

The correct answer is: The distance bgp 20 200 200 command is configured under the BGP process, increasing the AD of eBGP routes to 200. — The default administrative distance for eBGP is 20, and for OSPF is 110, so eBGP should be preferred. However, if the distance command is applied to the eBGP neighbor or the BGP process, it can increase the AD of eBGP routes, making them less preferred than OSPF.

What should I do if I get this 300-410 question wrong?

Are there clue words in this question I should notice?

Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

What is the key concept behind this question?

OSPF neighbours must agree on key parameters.

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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. A network engineer is troubleshooting a multi-homed BGP setup. R1 receives the prefix 10.1.1.0/24 from two eBGP peers: R2 (AS 100) and R3 (AS 200). The engineer configures the distance bgp 20 20 20 command on R1 to make all BGP routes have the same AD. However, R1 still prefers the route from R2 over R3. What is the most likely reason?

hard

A.The route from R2 has a lower MED than the route from R3.
✓ B.The route from R2 has a higher local preference than the route from R3.
C.The route from R2 is the oldest BGP route.
D.The AS path for the route from R2 is shorter than that from R3.

Why B: The distance bgp command sets AD for eBGP, iBGP, and local routes. With AD equal, the router uses other BGP path attributes, such as local preference, AS path length, or MED. The most common tie-breaker is local preference (default 100) or the oldest route.

Variation 2. An engineer is troubleshooting a network where R1 and R2 are running iBGP, and R1 learns the prefix 192.168.1.0/24 from R2 with an AD of 200. R1 also learns the same prefix via OSPF from R3 with AD 110. The engineer notices that R1 uses the iBGP route. What configuration change would cause this?

medium

A.The engineer applied the distance bgp 20 200 200 command, which lowers eBGP AD but not iBGP.
✓ B.The engineer applied the distance 150 0.0.0.0 255.255.255.255 under the OSPF process, raising OSPF AD to 150.
✓ C.The engineer applied the distance bgp 20 100 200 command, lowering iBGP AD to 100.
D.The OSPF route is a type 5 LSA, which has a higher AD than type 3 LSAs.

Why B: iBGP routes have an AD of 200 by default, which is higher than OSPF's 110, so OSPF should be preferred. If iBGP is preferred, the AD of iBGP must have been lowered or the OSPF AD raised.

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