200-901 Network Fundamentals Practice Question
At which layer of the OSI model do MAC addresses operate?
⚠ Common exam trap
Cisco often tests the confusion between Layer 2 MAC addresses and Layer 3 IP addresses, where candidates mistakenly associate MAC addresses with routing or network-layer functions instead of local data-link delivery.
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 2 – Data Link
MAC addresses operate at Layer 2 (Data Link) of the OSI model because they are used for local network addressing and frame delivery between directly connected devices. The Data Link layer encapsulates packets into frames and uses MAC addresses to identify source and destination interfaces on the same network segment, as defined by IEEE 802 standards.
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 2 – Data Link
Why this is correct
Correct. MAC addresses are Layer 2 identifiers.
- ✗
Layer 1 – Physical
Why it's wrong here
Layer 1 deals with bits and physical media.
- ✗
Layer 4 – Transport
Why it's wrong here
Layer 4 uses ports and segments.
- ✗
Layer 3 – Network
Why it's wrong here
Layer 3 uses IP addresses, not MAC addresses.
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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