- A
OSPFv3 does not use DR/BDR election; instead, it forms full mesh adjacencies.
Why wrong: OSPFv3 uses DR/BDR on broadcast.
- B
All routers on the network form full adjacencies with every other router.
Why wrong: Only DR/BDR form full adjacencies with all.
- C
The DR is elected based on the highest router ID, with a tiebreaker of highest interface priority.
Why wrong: Highest priority wins, then highest RID.
- D
The Designated Router (DR) is elected to reduce the number of adjacencies and LSDB flooding.
DR/BDR reduce O(n^2) to O(n).
Question 823 of 1,000
350-501 Networking Practice Question
This 350-501 practice question tests your understanding of networking. 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.
A service provider uses OSPFv3 for IPv6 routing in the core. Which statement correctly describes OSPFv3 adjacency formation on a broadcast multiaccess network?
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 Designated Router (DR) is elected to reduce the number of adjacencies and LSDB flooding.
OSPFv3 operates similarly to OSPFv2 on broadcast networks, electing a DR and BDR using Hello protocol, and forming adjacencies with the DR.
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.
- ✗
OSPFv3 does not use DR/BDR election; instead, it forms full mesh adjacencies.
Why it's wrong here
OSPFv3 uses DR/BDR on broadcast.
- ✗
All routers on the network form full adjacencies with every other router.
Why it's wrong here
Only DR/BDR form full adjacencies with all.
- ✗
The DR is elected based on the highest router ID, with a tiebreaker of highest interface priority.
Why it's wrong here
Highest priority wins, then highest RID.
- ✓
The Designated Router (DR) is elected to reduce the number of adjacencies and LSDB flooding.
Why this is correct
DR/BDR reduce O(n^2) to O(n).
Related concept
OSPF neighbours must agree on key parameters.
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.
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
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.
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FAQ
Questions learners often ask
What does this 350-501 question test?
Networking — This question tests Networking — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The Designated Router (DR) is elected to reduce the number of adjacencies and LSDB flooding. — OSPFv3 operates similarly to OSPFv2 on broadcast networks, electing a DR and BDR using Hello protocol, and forming adjacencies with the DR.
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.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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Last reviewed: Jul 4, 2026
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