- A
Layer 1 - Physical
Why wrong: Deals with bits and physical media, not addressing.
- B
Layer 3 - Network
Correct. Routing and IP addressing occur at Layer 3.
- C
Layer 4 - Transport
Why wrong: Handles TCP/UDP segments and reliability, not routing.
- D
Layer 2 - Data Link
Why wrong: Uses MAC addresses and switches, not IP routing.
Question 485 of 1,000
ISC2 CC Network Security Practice Question
This CC practice question tests your understanding of network security. 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 networks using IP addresses?
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. It uses IP addresses to determine the best path for packets to travel from source to destination across different networks. Protocols like IP (IPv4/IPv6), OSPF, and BGP operate at this layer to perform routing decisions.
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
Deals with bits and physical media, not addressing.
- ✓
Layer 3 - Network
Why this is correct
Correct. Routing and IP addressing occur at Layer 3.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Layer 4 - Transport
- ✗
Layer 2 - Data Link
Why it's wrong here
Uses MAC addresses and switches, not IP routing.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between Layer 2 switching (MAC-based forwarding within a VLAN) and Layer 3 routing (IP-based forwarding between subnets), so the trap here is confusing the Data Link layer's local delivery role with the Network layer's internetwork routing function.
Detailed technical explanation
How to think about this question
Routing at Layer 3 involves examining the destination IP address in the packet header and consulting a routing table (populated by static routes or dynamic protocols like OSPF, EIGRP, or BGP) to determine the next-hop interface. The router decrements the TTL field and recalculates the header checksum before forwarding. In real-world scenarios, misconfigured routing tables can cause black holes or routing loops, which are detected by mechanisms like TTL expiry and ICMP Time Exceeded messages.
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 security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
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
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FAQ
Questions learners often ask
What does this CC question test?
Network Security — This question tests Network Security — 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. It uses IP addresses to determine the best path for packets to travel from source to destination across different networks. Protocols like IP (IPv4/IPv6), OSPF, and BGP operate at this layer to perform routing decisions.
What should I do if I get this CC 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.
About these practice questions
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Last reviewed: Jul 4, 2026
This CC practice question is part of Courseiva's free ISC2 certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CC exam.
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