What a Network Really Is
A network is any collection of devices that can exchange data. Your homelab, your phone, your router — all participants in a structured conversation governed by protocols. Protocols are just agreed-upon rules: how to start a conversation, how to break data into pieces, how to confirm it arrived intact.
Without networks, every machine is an island. With them, a Proxmox host can manage 20 VMs, a Cloudflare tunnel can expose a local service to the internet, and a Pi-hole can intercept DNS requests before they leave your LAN.
Your Homelab Network — simplified
[Laptop]──┐
[Phone] ──┤──[Switch]──[Router]──[Firewall]──[Internet]
[Server]──┘ |
[Proxmox]
[NAS / VMs]The OSI Model — Why It Matters
The OSI model splits networking into 7 layers. You don't need to memorize all of them, but understanding the key layers helps you diagnose problems at the right level.
Layer 7 — Application HTTP, DNS, SSH, SMTP Layer 4 — Transport TCP (reliable), UDP (fast, no guarantee) Layer 3 — Network IP addresses, routing decisions Layer 2 — Data Link MAC addresses, switches, VLANs Layer 1 — Physical Cables, fiber, WiFi signals Troubleshooting tip: Can't ping? → Layer 3 problem (routing / IP) Ping works, HTTP fails? → Layer 7 problem (app / firewall rule) No link light? → Layer 1 problem (cable / NIC)
LAN, WAN, and VLAN
LAN (Local Area Network) — your internal network. Everything behind your router: servers, laptops, phones. Fast, trusted (usually), private.
WAN (Wide Area Network) — the internet, or any network outside your control. Treat all WAN traffic as hostile by default.
VLAN (Virtual LAN) — a way to logically separate devices on the same physical network. IoT devices on VLAN 20, servers on VLAN 10, management on VLAN 99 — they can't talk to each other unless you explicitly allow it.
Homelab VLAN example: VLAN 1 — Management (router, switch, Proxmox web UI) VLAN 10 — Servers / VMs VLAN 20 — IoT (cameras, smart plugs — untrusted) VLAN 30 — Personal devices (laptops, phones)
TCP vs UDP
Most traffic runs on one of two transport protocols. Choosing the right one is the application's job — but knowing the difference helps you understand why things behave the way they do.
TCP — Transmission Control Protocol ✓ Reliable: confirms every packet arrived ✓ Ordered: reassembles packets in sequence ✗ Slower: handshake + acknowledgment overhead → Used by: HTTP/S, SSH, SMTP, databases UDP — User Datagram Protocol ✓ Fast: fire-and-forget, no handshake ✗ Unreliable: no delivery guarantee → Used by: DNS, video streaming, VoIP, game traffic
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