Section 1
Network Basics
Preview
Preview: Network Fundamentals
- 4 of 22 lesson topics
- 1 overview segment
- 3 core concepts
- 2 exam tips
Lesson Topics
- Layer 3 Switching and Inter-VLAN Routing
- Firewall Traffic Policy
- Spine-Leaf Data Center Topology
- Three-Tier Campus Topology
Overview
This section covers the CCNA network-fundamentals skills behind device roles, common architectures, cabling choices, Ethernet behavior, transport protocols, IPv4 subnetting, and IPv6 addressing. The emphasis is on choosing and troubleshooting the right concept from the stated constraints rather than memorizing labels.
Core Concepts
- **Device Roles:** Routers connect IP networks and choose Layer 3 paths. Layer 3 switches can also route, commonly at high speed between VLANs, while Layer 2 switches forward frames within VLANs and firewalls enforce traffic policy.
- **Architectures and Cabling:** Spine-leaf is common in data centers for predictable east-west paths; three-tier designs use access, distribution, and core layers. Single-mode fiber supports longer reaches, while multimode is common for shorter building or data-center runs.
- **Ethernet Negotiation:** Duplex and speed problems produce symptoms such as errors, drops, slow throughput, or failed links. Collisions are a classic half-duplex symptom, but modern switched Ethernet behavior depends on the negotiated or configured mode and platform support.
Exam Tips
- Read the device role before choosing the device name. A switch, router, firewall, or Layer 3 switch can all appear in similar-looking scenarios.
- Do not solve Ethernet symptoms from one keyword. Check whether the issue is speed, duplex, cabling, negotiation, or interface configuration.