Simple explanation
This lesson catalogs the physical and virtual boxes that make up a network, and what each one's actual job is.
Technical explanation
- Switch — connects devices within a LAN, forwards frames based on MAC address (Layer 2).
- Router — connects different networks, forwards packets based on IP address (Layer 3).
- Firewall — enforces traffic policy, allowing/denying based on rules.
- Access point (AP) — provides wireless connectivity, bridging wireless clients to the wired network.
- Wireless LAN controller (WLC) — centrally manages multiple access points.
- Load balancer — distributes traffic across multiple servers.
- Proxy server — intermediary for client requests, can cache, filter, and anonymize.
- IDS/IPS — detects (IDS) or detects-and-blocks (IPS) malicious traffic.
- Network Attached Storage (NAS) — file-level shared storage accessible over the network.
- Content delivery network (CDN) — geographically distributed servers caching content closer to end users, reducing latency.
- VoIP gateway — bridges traditional telephone systems and IP-based voice traffic.
- Media converter — translates between different physical media types (e.g., fiber to copper).
- Voice gateway, modem, repeater/extender — extend or convert signal for specific media/purposes.
Understanding placement — where in the network topology each of these belongs — matters as much as knowing what each device does.
Synonyms / related terms
| Term | Means | |---|---| | WLC | Wireless LAN Controller | | NAS | Network Attached Storage | | CDN | Content Delivery Network |
Concept Check
"A company wants to reduce load on its origin web server by serving static images from locations physically closer to users around the world." This is a CDN use case specifically, not a simple load balancer — a load balancer distributes traffic across servers you own in one or few locations, while a CDN's defining feature is geographic distribution to reduce latency for globally dispersed users.
Interview-style Q&A
Q: What's the practical difference between an IDS and IPS in terms of placement? A: "An IDS is typically deployed out-of-band, receiving a mirrored copy of traffic via a tap or SPAN port — it can alert but never touches the live path. An IPS has to be inline, directly in the traffic's path, because blocking requires actually sitting between the source and destination. That placement difference is also why an IPS carries more risk if misconfigured — it can disrupt legitimate traffic in a way an IDS structurally cannot."
Memory trick
"Switch locally, Router globally, Firewall always" — a quick reminder that switches operate within a LAN, routers connect between networks, and firewalls enforce policy regardless of which layer the traffic is crossing.