- A
EIGRP external routes (redistributed) have a default administrative distance of 170.
Correct: EIGRP uses AD 170 for external routes, while internal routes use 90.
- B
OSPF external routes (type 1 and type 2) have a default administrative distance of 110.
Correct: OSPF uses AD 110 for both internal and external routes by default.
- C
Adjusting administrative distance can be used to influence route selection and prevent routing loops during redistribution.
Correct: Changing AD can make one protocol's routes preferred over another, helping to avoid loops.
- D
The 'distance' command in OSPF can only be applied to external routes, not internal routes.
Why wrong: Incorrect: The distance command in OSPF can be applied to both internal and external routes.
- E
When redistributing RIP into OSPF, the redistributed routes will have a lower administrative distance than OSPF internal routes.
Why wrong: Incorrect: OSPF internal routes have AD 110, and redistributed routes also have AD 110 (or can be changed). RIP has AD 120, so redistributed routes from RIP into OSPF will have OSPF's AD.
Quick Answer
The correct answer is that adjusting administrative distance can be used to influence route selection and prevent routing loops during redistribution. This is because administrative distance (AD) is a trustworthiness metric that Cisco routers use to choose between routes learned from different routing protocols; when redistributing routes, the default AD for the redistributed protocol applies, which can cause suboptimal path selection or loops if not tuned. For the Cisco CCNP ENARSI 300-410 exam, you must know the default administrative distance for redistributed routes: EIGRP external routes default to 170, OSPF external routes default to 110 (same as internal), and RIP defaults to 120. A common trap is assuming OSPF external routes have a higher AD than internal ones—they do not by default, but you can change them with the distance command. Memory tip: think of EIGRP as having a “90-170 split” (internal-external), while OSPF keeps a flat 110 for both.
300-410 Route Redistribution Practice Question
This 300-410 practice question tests your understanding of route redistribution. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Which THREE statements about route redistribution and administrative distance are true? (Choose THREE.)
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
EIGRP external routes (redistributed) have a default administrative distance of 170.
Administrative distance (AD) is crucial in redistribution because it determines which routes are preferred when multiple protocols learn the same prefix. Option A is correct: EIGRP has a default AD of 90 for internal routes and 170 for external (redistributed) routes. Option B is correct: OSPF external routes have a default AD of 110, same as internal OSPF routes, but can be changed. Option C is correct: Changing AD can influence route selection and help prevent routing loops. Option D is incorrect: The distance command can be applied to both internal and external routes. Option E is incorrect: RIP has a default AD of 120, which is higher than OSPF's 110, so OSPF is preferred.
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.
- ✓
EIGRP external routes (redistributed) have a default administrative distance of 170.
- ✓
OSPF external routes (type 1 and type 2) have a default administrative distance of 110.
- ✓
Adjusting administrative distance can be used to influence route selection and prevent routing loops during redistribution.
- ✗
The 'distance' command in OSPF can only be applied to external routes, not internal routes.
- ✗
When redistributing RIP into OSPF, the redistributed routes will have a lower administrative distance than OSPF internal routes.
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
Command / output trap
Incorrect: The distance command in OSPF can be applied to both internal and external routes.
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?
Route Redistribution — This question tests Route Redistribution — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: EIGRP external routes (redistributed) have a default administrative distance of 170. — Administrative distance (AD) is crucial in redistribution because it determines which routes are preferred when multiple protocols learn the same prefix. Option A is correct: EIGRP has a default AD of 90 for internal routes and 170 for external (redistributed) routes. Option B is correct: OSPF external routes have a default AD of 110, same as internal OSPF routes, but can be changed. Option C is correct: Changing AD can influence route selection and help prevent routing loops. Option D is incorrect: The distance command can be applied to both internal and external routes. Option E is incorrect: RIP has a default AD of 120, which is higher than OSPF's 110, so OSPF is preferred.
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.
About these practice questions
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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. What is the default administrative distance for routes redistributed into EIGRP from another protocol?
medium- A.90
- B.110
- ✓ C.170
- D.200
Why C: By default, EIGRP assigns an administrative distance of 170 to routes learned via redistribution, distinguishing them from internal EIGRP routes (AD 90) and external EIGRP routes (AD 170).
Variation 2. What is the default administrative distance for routes redistributed into BGP from an IGP?
medium- ✓ A.20
- B.110
- C.170
- D.200
Why A: Routes redistributed into BGP from an IGP are considered external BGP (eBGP) routes and have a default administrative distance of 20.
Last reviewed: Jun 18, 2026
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