L1/L2
COMPONENT 01
Endpoints & Network Adapters
Hosts, NICs, MAC addresses, interface states, speed/duplex and the endpoint side of a packet path.
Open Playbook L2 & L3 Component Fundamentals
Know the components.
Understand the path.
A component-first learning module for L2 and L3 engineers. Learn what each network component does, where it sits in the architecture, what state it maintains, how it forwards traffic and how to troubleshoot it in production.
01 · Component Map
From the physical link to the enterprise edge.
Do not learn network devices as isolated product names. Learn their responsibility, state, interfaces and place in the packet journey. Open a playbook whenever you need a focused revision before moving forward.
L1
COMPONENT 02
Cabling & Transceivers
Copper, fiber, optics, SFP/SFP+, media types, distance, polarity and physical-layer failure symptoms.
Open PlaybookL1/L2
COMPONENT 03
Hub vs Switch
Understand why hubs repeat bits while switches learn MAC addresses and make forwarding decisions.
Open PlaybookL2
COMPONENT 04
Layer 2 Switches
Access ports, trunks, CAM tables, VLANs, STP, EtherChannel and the switching data plane.
Open PlaybookL2/L3
COMPONENT 05
Layer 3 Switches
SVIs, routed ports, hardware forwarding and where campus switching becomes routing.
Open PlaybookL3
COMPONENT 06
Routers
Interfaces, routing tables, next hops, control plane vs data plane and inter-network forwarding.
Open PlaybookL3/Security
COMPONENT 07
Firewalls
Stateful inspection, zones, security policy, NAT and how firewall decisions affect packet flow.
Open PlaybookL2/WLAN
COMPONENT 08
Wireless Access Points
SSID, radio, channel, client association, VLAN mapping and the wired path behind an AP.
Open PlaybookL2/L3
COMPONENT 09
Wireless Controllers
Centralized policy, AP management, roaming, tunnels and enterprise WLAN architecture.
Open PlaybookL4/L7
COMPONENT 10
Load Balancers
Virtual services, health checks, VIPs, persistence and the difference between network and application forwarding.
Open PlaybookL2/L3
COMPONENT 11
WAN / Internet Edge
ONT/modem, edge router, provider handoff, BGP and the operational boundary between enterprise and carrier.
Open PlaybookL3/Security
COMPONENT 12
Network Security Sensors
IDS/IPS, visibility points, telemetry and how security controls become part of the packet path.
Open Playbook02 · Engineering Thinking
Every component should answer six questions.
01
What is it?
Identify the component, interface type, operating layer and primary responsibility.
02
Where is it?
Place it correctly in the topology and identify its neighboring devices.
03
What does it know?
Determine whether it uses MAC, VLAN, ARP, routing, session or policy state.
04
How does it forward?
Explain the decision that moves traffic to the next interface or hop.
05
How can it fail?
Predict the observable symptoms before touching the configuration.
06
How do I prove it?
Choose counters, status commands, logs or packet captures that provide evidence.
03 · Component Labs
Turn recognition into troubleshooting skill.
Each exercise connects component knowledge to evidence collection and packet-flow reasoning.
01
Identify the Packet Path
Given an enterprise topology, identify every component a packet crosses from endpoint to application.
02
Switch or Router?
Determine whether a forwarding problem belongs to VLAN/MAC logic or IP/routing logic.
03
Physical-to-Logical Fault Isolation
Start with a link-down symptom and isolate cable, optic, interface, VLAN and gateway causes.
04
Firewall in the Path
Trace a permitted and denied flow through zones, NAT and security policy.
05
Enterprise Edge Walkthrough
Explain the path from campus access through distribution, edge routing, provider handoff and Internet.