Demo lesson — OSI layers
This is sample content for the public portfolio shell. It shows how MDX lessons render in the app without exposing the full CCNA curriculum.
Info
Full lesson content is available in the private course version.
Why layers matter
Networks are easier to troubleshoot when you know which layer a problem belongs to:
- Physical — bits on the wire
- Data Link — MAC addresses, switches, VLANs
- Network — IP addresses, routers
- Transport — TCP or UDP ports
- Session — dialog control (less tested on CCNA)
- Presentation — encoding/compression
- Application — HTTP, DNS, SSH
Quick check
Which device primarily operates at Layer 2?
Try the interactive tools
Open the PacketStack lab to step through encapsulation with sample scenarios.