Fundamentals

Networking fundamentals and CCNA-level reference content. The TCP/IP and OSI models, ethernet basics, encapsulation, IPv4 addressing, layer 2 fundamentals, and the Cisco IOS commands every network engineer reaches for. The foundations beneath the pillar guides.

76 posts

VLAN

Inter-VLAN Routing: SVI vs Router-on-a-Stick (with Real IOS XE Config)

The two ways to route between VLANs on Cisco: SVIs on an L3 switch and router-on-a-stick. Real IOS XE config for both, the performance gap, and the gotchas.

May 22, 2026 5 min read

MPLS

MPLS L3VPN vs SD-WAN: When to Migrate

A decision framework for migrating from MPLS L3VPN to SD-WAN: what's different, when to migrate, the 7-step transition that works, and when the right answer is to stay.

May 21, 2026 5 min read

BGP looking glass feature image, PingLabz

BGP

BGP Looking Glass: What It Is, Public Servers, and Hosting Your Own

BGP looking glasses explained: what they show, the public servers worth bookmarking, a four-step troubleshooting recipe, and how to host your own with hyperglass.

May 21, 2026 5 min read

OSPF

OSPF Adjacency States: The 8-State FSM, Explained

All 8 OSPF neighbor states (Down, Attempt, Init, 2-Way, ExStart, Exchange, Loading, Full), what triggers each transition, and what to check when a neighbor is stuck.

May 20, 2026 6 min read

VLAN

VLAN, Subnet, and Broadcast Domain: What's the Difference?

VLAN, subnet, and broadcast domain are not the same thing. The layer each lives at, the relationships between them, and the misalignment that breaks hosts silently.

May 20, 2026 5 min read

SD-WAN

SD-WAN: What Is It? The 5-Minute Primer

SD-WAN in five minutes: what it is, what it replaces, the four-plane architecture, transport-independent overlays, and how it stacks against traditional MPLS WANs.

May 19, 2026 5 min read