What is OSI model?
A seven-layer way of describing how data travels across a network.
In plain English
The layers, from the bottom up, are Physical, Data Link, Network, Transport, Session, Presentation and Application. Each layer has one job and talks only to the layers next to it. The model is a teaching and troubleshooting tool: it helps you say where a problem is, such as a loose cable (layer 1) or a wrong IP address (layer 3).
Example
A switch normally works at layer 2 using MAC addresses. A router works at layer 3 using IP addresses. TCP and UDP sit at layer 4.
Where you will meet it
This idea belongs to the subject area of these practice tests. We do not publish or predict real exam questions.
- Cisco CCST Networking practice tests
- CompTIA Tech+ practice tests
- Cisco CCST IT Support practice tests
Related terms
- DNS: The system that turns names like example.com into the IP addresses computers use.
- DHCP: The service that automatically gives devices an IP address and other network settings.
- Subnet: A smaller network carved out of a larger IP range.
Test yourself
Practice tests with an explanation for every answer option, so each mistake teaches you something.
Browse practice testsAll glossary termsWritten and checked by the Be Ready Education team, last reviewed 2 November 2026. General study information, not professional advice. Providers change names and rules, so confirm details on the official documentation. Not affiliated with, endorsed by or sponsored by any certification vendor or exam body. Certification names, exam codes and product names are trademarks of their respective owners and are used only to identify the exam a practice product prepares for. Our questions are original and are not actual exam questions.