Question 363 of 1,000

Network Fundamentals →easyMultiple ChoiceObjective-mapped

200-901 Network Fundamentals Practice Question

This 200-901 practice question tests your understanding of network fundamentals. 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 OSI layer is responsible for routing packets across different networks?

A
Layer 1 (Physical)
Why wrong: Layer 1 deals with raw bit transmission over physical media.
B
Layer 3 (Network)
Layer 3 uses IP addresses to route packets across networks.
C
Layer 4 (Transport)
Why wrong: Layer 4 provides end-to-end communication and reliability.
D
Layer 2 (Data Link)
Why wrong: Layer 2 handles frame switching within the same network segment.

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

✓

Layer 3 (Network)

The Network layer (Layer 3) is responsible for logical addressing and routing packets between different networks. Protocols like IP (IPv4/IPv6) use routing tables and algorithms (e.g., OSPF, BGP) to determine the best path for forwarding packets across multiple hops. Without Layer 3, traffic could not leave a local broadcast domain.

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.

✗
Layer 1 (Physical)
Why it's wrong here
Layer 1 deals with raw bit transmission over physical media.
✓
Layer 3 (Network)
Why this is correct
Layer 3 uses IP addresses to route packets across networks.
Related concept
Read the scenario before looking for a memorised answer.
✗
Layer 4 (Transport)
Why it's wrong here
Layer 4 provides end-to-end communication and reliability.
✗
Layer 2 (Data Link)
Why it's wrong here
Layer 2 handles frame switching within the same network segment.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the distinction between Layer 2 switching (MAC-based, same network) and Layer 3 routing (IP-based, between networks), and the trap here is confusing the Data Link layer's local forwarding with the Network layer's internetwork routing.

Detailed technical explanation

How to think about this question

Routing at Layer 3 involves examining the destination IP address, performing a longest-prefix match against the routing table, and decrementing the TTL (Time to Live) field in the IP header. In a real-world scenario, when a packet leaves a home router, the router strips the Layer 2 frame, inspects the Layer 3 header, and forwards the packet to the next-hop router based on its routing table—this process repeats until the packet reaches the destination network.

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.

Visual reference

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.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this 200-901 question test?

Network Fundamentals — This question tests Network Fundamentals — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Layer 3 (Network) — The Network layer (Layer 3) is responsible for logical addressing and routing packets between different networks. Protocols like IP (IPv4/IPv6) use routing tables and algorithms (e.g., OSPF, BGP) to determine the best path for forwarding packets across multiple hops. Without Layer 3, traffic could not leave a local broadcast domain.

What should I do if I get this 200-901 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: Jul 4, 2026

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