- A
The OSPF network type is point-to-point, so the hello interval defaults to 10 seconds on this interface.
On a point-to-point network type, the default OSPF hello interval is 10 seconds (same as broadcast). This is correct.
- B
The OSPF network type is point-to-point, so the dead interval defaults to 120 seconds.
Why wrong: The default dead interval for point-to-point is 40 seconds (4x hello of 10 seconds), not 120 seconds.
- C
The redistribution of BGP into OSPF will cause OSPF to advertise all BGP routes, including those learned via SD-WAN overlay.
Why wrong: Redistribution of BGP into OSPF will redistribute BGP routes, but OSPF will only advertise routes that match the network statement or are redistributed. However, the statement is too broad and may not be accurate for all BGP routes; also, SD-WAN overlay routes are typically in a separate VRF.
- D
The configuration is incomplete because OSPF requires a router-id to be manually configured.
Why wrong: OSPF can automatically select a router-id from the highest loopback or physical interface IP. Manual configuration is not required.
Quick Answer
The answer is that the OSPF hello interval defaults to 10 seconds on a point-to-point interface in an SD-WAN configuration. This is correct because Cisco IOS-XE routers automatically set the hello interval to 10 seconds when the network type is configured as point-to-point, unlike broadcast networks which default to 30 seconds; the dead interval then becomes 40 seconds, calculated as four times the hello interval. On the ENCOR 350-401 exam, this question tests your understanding of OSPF network type behavior in SD-WAN contexts, often appearing as a trap where candidates mistakenly recall the broadcast default of 30 seconds or confuse the dead interval with 120 seconds. A key memory tip is "point-to-point, ten is sent"—remember that point-to-point links use a 10-second hello, while broadcast networks use 30 seconds, and the dead interval is always four times the hello.
CCNP SD-WAN Architecture Practice Question
This 350-401 practice question tests your understanding of sd-wan architecture. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Given the following SD-WAN configuration on a Cisco IOS-XE router:
router ospf 1
redistribute bgp 65000 subnets
network 192.168.1.0 0.0.0.255 area 0
!
interface GigabitEthernet0/0/0 ip address 192.168.1.1 255.255.255.0 ip ospf network point-to-point
!
Which statement is true?
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 OSPF network type is point-to-point, so the hello interval defaults to 10 seconds on this interface.
Option A is correct because on a Cisco IOS-XE router, when the OSPF network type is set to point-to-point, the default hello interval is 10 seconds (not 30 seconds as on broadcast networks). The dead interval defaults to 40 seconds (four times the hello interval), not 120 seconds. This configuration is valid and does not require a manually configured router-id, as OSPF can dynamically select one. The redistribution of BGP into OSPF only injects routes that are in the BGP table; it does not automatically include all SD-WAN overlay routes unless they are present in BGP.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 network type is point-to-point, so the hello interval defaults to 10 seconds on this interface.
Why this is correct
On a point-to-point network type, the default OSPF hello interval is 10 seconds (same as broadcast). This is correct.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The OSPF network type is point-to-point, so the dead interval defaults to 120 seconds.
Why it's wrong here
The default dead interval for point-to-point is 40 seconds (4x hello of 10 seconds), not 120 seconds.
- ✗
The redistribution of BGP into OSPF will cause OSPF to advertise all BGP routes, including those learned via SD-WAN overlay.
Why it's wrong here
Redistribution of BGP into OSPF will redistribute BGP routes, but OSPF will only advertise routes that match the network statement or are redistributed. However, the statement is too broad and may not be accurate for all BGP routes; also, SD-WAN overlay routes are typically in a separate VRF.
- ✗
The configuration is incomplete because OSPF requires a router-id to be manually configured.
Why it's wrong here
OSPF can automatically select a router-id from the highest loopback or physical interface IP. Manual configuration is not required.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the default OSPF timer values for different network types, specifically tricking candidates into thinking point-to-point uses 30-second hello or 120-second dead intervals, which are actually defaults for NBMA networks.
Detailed technical explanation
How to think about this question
Under the hood, the OSPF hello and dead intervals are tied to the network type: point-to-point networks use a 10-second hello and 40-second dead interval (RFC 2328), while broadcast networks use 10-second hello and 40-second dead intervals as well, but NBMA networks default to 30-second hello and 120-second dead intervals. The trap often involves confusing NBMA defaults with point-to-point. In SD-WAN environments, OSPF is commonly used for underlay routing, and redistribution of BGP (which carries overlay routes) must be carefully filtered to avoid injecting excessive prefixes into the underlay.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
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FAQ
Questions learners often ask
What does this 350-401 question test?
SD-WAN Architecture — This question tests SD-WAN Architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The OSPF network type is point-to-point, so the hello interval defaults to 10 seconds on this interface. — Option A is correct because on a Cisco IOS-XE router, when the OSPF network type is set to point-to-point, the default hello interval is 10 seconds (not 30 seconds as on broadcast networks). The dead interval defaults to 40 seconds (four times the hello interval), not 120 seconds. This configuration is valid and does not require a manually configured router-id, as OSPF can dynamically select one. The redistribution of BGP into OSPF only injects routes that are in the BGP table; it does not automatically include all SD-WAN overlay routes unless they are present in BGP.
What should I do if I get this 350-401 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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