ISC2 CC Network Security Practice Question
Which OSI layer is responsible for routing packets across networks using IP addresses?
⚠ Common exam trap
A common pitfall is confusing the Data Link layer's local delivery role (Layer 2) with the Network layer's internetwork routing function (Layer 3). Remember that routing across networks using IP addresses occurs at Layer 3.
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.
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 transmits raw bits as electrical, optical or radio signals across the physical medium; it has no concept of IP addresses or forwarding decisions. Physical is tempting as the foundation carrying all traffic, but it would be correct for cabling, connectors and signalling questions.
- ✓
Layer 3 - Network
Why this is correct
Layer 3, the Network layer, handles logical addressing and path selection, so routers use IP addresses to forward packets between distinct networks. Layers 2 and 4 lack routable addressing, making Layer 3 the layer that satisfies the routing requirement in the stem.
- ✗
Layer 4 - Transport
Why it's wrong here
Layer 4 segments, sequences and delivers data between endpoints using ports and protocols such as TCP and UDP; it never inspects IP addresses to forward packets between networks. Transport is tempting because TCP and UDP carry the traffic, but it would be correct for port-based questions, not routing.
- ✗
Layer 2 - Data Link
Why it's wrong here
Layer 2 frames data and forwards it using MAC addresses within a single broadcast domain; IP-based path selection between networks occurs above it. Data Link is tempting because switches forward frames, but it would be correct for MAC addressing, VLANs or error detection on a local segment.
Visual reference
Go deeper
Related to this question
About these practice questions
This CC question is part of Courseiva's 989-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.