Which OSI Layer Handles Logical Addressing and Routing?
At which layer of the OSI model does logical addressing (e.g., IP addresses) and routing occur?
Quick Answer
The Network layer is correct because logical addressing and routing are defined specifically at Layer 3 of the OSI model, which sits above the Data Link layer's physical, hardware-based addressing and handles addressing that can be organized hierarchically and reassigned independent of physical hardware. IP addresses are the clearest example of this: they're structured so that routers can group them by network and make forwarding decisions based on which network a destination belongs to, rather than needing to know the physical location of every individual device. Routers are the devices that live at this layer, using routing tables built from protocols or static configuration to determine the best path for a packet to reach a destination that may be many networks away, and this layer is also responsible for handling situations where a packet needs to be fragmented and later reassembled to cross networks with different size limits. This is distinct from the Data Link layer, which only handles addressing and delivery within a single local network segment. Whenever an exam question mentions IP addressing, routing between networks, or path selection across multiple networks, that combination of logical addressing and inter-network delivery is the signature of the OSI Network layer.
⚠ Common exam trap
It's easy for candidates to confuse the Network layer's logical addressing with the Data Link layer's MAC addressing, especially when they see 'addressing' in the question and default to Layer 2 without considering the 'routing' keyword that clearly points to 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
✓
Network layer
The Network layer (Layer 3) of the OSI model is responsible for logical addressing, such as IPv4 and IPv6 addresses, and for routing packets between different networks. Routers operate at this layer, using routing tables and protocols like OSPF, BGP, or static routes to determine the best path for data. This layer provides end-to-end delivery and handles packet fragmentation and reassembly when necessary.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Data Link layer
Why it's wrong here
The Data Link layer (Layer 2) handles physical addressing (MAC addresses) and switching within a local network.
When this WOULD be correct
This option would be correct for a question asking: 'At which OSI layer does physical addressing (MAC addresses) and switching occur?' or 'Which layer is responsible for error detection in frames using CRC?'
- ✓
Network layer
Why this is correct
The Network layer (Layer 3) uses IP addresses for logical addressing and routing decisions.
- ✗
Transport layer
Why it's wrong here
The Transport layer (Layer 4) provides reliable or unreliable delivery and segmentation, not routing.
When this WOULD be correct
A question asking 'At which layer does port addressing (e.g., TCP/UDP ports) and segmentation occur?' would have the Transport layer as the correct answer.
- ✗
Physical layer
Why it's wrong here
The Physical layer (Layer 1) defines hardware specifications like cables and signals.
When this WOULD be correct
A question asking 'At which layer do physical network interface specifications (e.g., voltage levels, cable types, and data rates) reside?' would have the Physical layer as the correct answer.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓Network layerCorrect answer▾
Why this is correct
The Network layer (Layer 3) uses IP addresses for logical addressing and routing decisions.
✗Data Link layerWrong answer — click to see why▾
Why this is wrong here
Logical addressing (IP addresses) and routing are functions of the Network layer (Layer 3), not the Data Link layer (Layer 2), which handles physical addressing (MAC addresses) and frame forwarding within a local network.
★ When this WOULD be the correct answer
This option would be correct for a question asking: 'At which OSI layer does physical addressing (MAC addresses) and switching occur?' or 'Which layer is responsible for error detection in frames using CRC?'
Why candidates choose this
Candidates often confuse the Data Link layer's role in local network addressing (MAC) with the Network layer's global logical addressing (IP), especially when they think of 'addressing' broadly without distinguishing between logical and physical.
✗Transport layerWrong answer — click to see why▾
Why this is wrong here
The Transport layer (Layer 4) is responsible for end-to-end communication, segmentation, and flow control, not logical addressing or routing. IP addresses and routing are functions of the Network layer (Layer 3).
★ When this WOULD be the correct answer
A question asking 'At which layer does port addressing (e.g., TCP/UDP ports) and segmentation occur?' would have the Transport layer as the correct answer.
Why candidates choose this
Candidates may confuse the Transport layer's role in managing connections (like TCP) with the Network layer's addressing, or mistakenly think that IP addresses are part of transport protocols.
✗Physical layerWrong answer — click to see why▾
Why this is wrong here
The Physical layer (Layer 1) is responsible for the transmission and reception of raw bit streams over a physical medium, not for logical addressing or routing.
★ When this WOULD be the correct answer
A question asking 'At which layer do physical network interface specifications (e.g., voltage levels, cable types, and data rates) reside?' would have the Physical layer as the correct answer.
Why candidates choose this
Candidates may confuse the Physical layer with the Network layer because both involve 'addresses' (MAC vs. IP) or think that routing requires physical connectivity.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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.
Go deeper
Related to this question
Learn chapter
Interior vs Exterior Routing Protocols
Key term
OSI model
The OSI model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven distinct layers, from physical hardware to application software.
Key term
BGP
BGP (Border Gateway Protocol) is the routing protocol that directs data packets across the internet by choosing the best paths between autonomous systems.
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Same concept, more angles
1 more way this is tested on N10-009
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which layer of the OSI model is responsible for logical addressing and routing of packets between networks?
easy- A.Data Link layer
- ✓ B.Network layer
- C.Transport layer
- D.Application layer
Why B: The Network layer (Layer 3) is responsible for logical addressing (e.g., IPv4/IPv6 addresses) and routing packets between different networks by determining the best path using routing protocols such as OSPF, BGP, or static routes. Unlike the Data Link layer, which handles physical addressing (MAC) within a single network segment, the Network layer enables end-to-end delivery across multiple hops.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This N10-009 practice question is part of Courseiva's free CompTIA 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 N10-009 exam.