Objective 1.1
N10-009Explain concepts related to the Open Systems Interconnection (OSI) reference model.
Objective 1.1 sits in Networking Concepts, which carries 23% of the Network+ exam. The questions below are original, written from the official objective title above, and each explanation cites the CompTIA page it rests on.
Objective title verbatim from the official objectives. CompTIA exam page ↗
A worked example
Shown solved, with the whole explanation open: this is what every question here carries.
A network technician captures traffic and finds a router sending ICMP Destination Unreachable messages back to a source host after failing to forward one of its packets toward the destination network. Which OSI layer generates these messages?
Correct.
Checked against datatracker.ietf.org, August 2026Concept
The network layer is responsible for logical addressing, routing, and reporting delivery problems for datagrams as they move between networks.
Why A
ICMP error messages such as Destination Unreachable are generated as part of the network layer's job of reporting forwarding failures for IP datagrams.
Source
RFC 1122: Requirements for Internet Hosts, checked August 20263. INTERNET LAYER PROTOCOLS.................................... 27... 3.2.2 Internet Control Message Protocol -- ICMP.......... 38 3.2.2.1 Destination Unreachable...................... 39…
Now you: objective 1.1 questions
No account needed. The explanation opens when you answer.
Sample question 1 of 3
During a packet capture review, an analyst notices two hosts negotiating a maximum segment size and exchanging sequence numbers to guarantee ordered, reliable delivery of a byte stream between their applications. Which OSI layer performs this function?
Sample question 2 of 3
A protocol stack documents four layers instead of the OSI model's seven, and folds OSI's top layers into one. Which two OSI layers does that single layer combine?
Sample question 3 of 3
An application sends IP datagrams to destinations whose capabilities are unknown. RFC 791 states every host must be prepared to accept datagrams up to what size?
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Read the sources
These are the official pages the questions above cite. Reading them is studying the objective from the primary source, which is what the explanations point you toward anyway.
More objectives in Networking Concepts
- 1.2 Compare and contrast networking appliances, applications, and functions.
- 1.3 Summarize cloud concepts and connectivity options.
- 1.4 Explain common networking ports, protocols, services, and traffic types.
- 1.5 Compare and contrast transmission media and transceivers.
- 1.6 Compare and contrast network topologies, architectures, and types.
- 1.7 Given a scenario, use appropriate IPv4 network addressing.
- 1.8 Summarize evolving use cases for modern network environments.