Every CCNA candidate memorizes the OSI seven-layer model and the four-layer TCP/IP model. The exam tests both. What students rarely get is a clear answer to: "okay - which show command lives at which layer?" This lab maps the model directly to the Cisco IOS XE commands you reach for every day, so the abstract layers stop feeling like trivia and start feeling like a diagnostic checklist.
What you will learn
- The OSI seven-layer model and the TCP/IP four-layer model, side by side
- Which Cisco show command exposes which layer's state
- How to read
show interfaces ethernet 0/0as a Layer 1 + Layer 2 status report - How to read
show ip interface ethernet 0/0as a Layer 3 status report - Why
show ip arpsits squarely between L2 and L3 (it is the binding) - The layer-by-layer escalation path from "ping fails" to "fault localized"
What this lab does NOT cover
- Application-layer (L7) diagnostics. Out of scope for CCNA.
- Encryption/IPsec layers. Lab sec-09 covers those.
- The full TCP/IP protocol suite. We focus on the layers visible in CLI output.
The two models side by side
Application
OSI Layer7
TCP/IP layerApplication
Cisco show command (primary)
(out of scope for CCNA)
Presentation
OSI Layer6
TCP/IP layerApplication
Cisco show command (primary)(out of scope)
Session
OSI Layer5
TCP/IP layerApplication
Cisco show command (primary)(out of scope)
Transport
OSI Layer4
TCP/IP layerTransport
Cisco show command (primary)
show tcp brief, show ip socketsNetwork
OSI Layer3
TCP/IP layerInternet
Cisco show command (primary)
show ip route, show ip interface, ping, tracerouteData Link
OSI Layer2
TCP/IP layerNetwork Access
Cisco show command (primary)
show mac address-table, show ip arp, show interfaces (line protocol)Physical
OSI Layer1
TCP/IP layerNetwork Access
Cisco show command (primary)
show interfaces (status), show controllersThe CCNA exam tests both models. In practice every engineer uses OSI for talking about faults ("we have a Layer 1 issue") and TCP/IP for talking about protocols ("HTTPS uses TLS over TCP over IP").
