Network Devices — Full Notes

This topic is about the physical boxes that make a network work. Good news: you've used most of these in your lab, so a lot will click fast. Let's go from simplest to smartest.

Hub (dumb, outdated):
A hub connects devices but has no intelligence. When data comes in, it blindly copies it out to every port — even devices it wasn't meant for. This wastes bandwidth and is insecure (everyone sees everything). Operates at Layer 1 (Physical). Basically obsolete now, replaced by switches. Hook: a hub is a "dumb repeater."

Switch (smart, Layer 2):
A switch also connects devices, but it's intelligent — it learns the MAC address of each device and sends data only to the correct port, not everywhere. This is what makes it far better than a hub. Operates at Layer 2 (Data Link). Your UniFi switch is exactly this — and remember, VLANs live here. Hook: switch = MAC addresses = Layer 2.

Router (connects networks, Layer 3):
A router connects different networks together and forwards traffic between them using IP addresses. This is what moves data between your VLANs, or between your home network and the internet. Operates at Layer 3 (Network). Your pfSense box did routing. Hook: router = IP addresses = Layer 3 = routing.

Firewall (security guard):
A firewall filters traffic based on rules — deciding what's allowed to pass and what gets blocked. It's the security checkpoint between networks. pfSense was your firewall — remember writing rules like "allow VLAN 20 to reach Splunk on 9997, block everything else." Firewalls often operate at Layers 3–4 (and modern ones higher). Hook: firewall = rules = allow/block.

Access Point (AP) — Wi-Fi:
An access point provides wireless (Wi-Fi) connectivity, letting wireless devices join the wired network. It bridges wireless devices onto the network. Hook: AP = Wi-Fi.

Modem:
A modem connects your network to your ISP — it modulates/demodulates signals, translating between your ISP's signal (cable, fiber, DSL) and your network's digital data. It's the box where the internet "enters" your house.

The Key Progression (exam gold)

The classic exam question: Hub vs Switch — "A hub sends data to all ports; a switch sends data only to the intended port using MAC addresses." Know that cold.