Which one of the following is not a network device ?
2009
Which one of the following is not a network device ?
Answer: D. CPU — Concept — A network device is hardware whose job is to move data between machines: it takes traffic in on one port and regenerates, filters or forwards it on…
- A.
Router
- B.
Switch
- C.
Hub
- D.
CPU
Attempted by 254 students.
Show answer & explanation
Correct answer: D
Concept — A network device is hardware whose job is to move data between machines: it takes traffic in on one port and regenerates, filters or forwards it on towards another machine. Hardware that only processes or stores data inside a single computer serves that one machine's own computation and sits nowhere on the path between machines.
Application — Apply that test to each item in the list — where does it sit, and what does it do with traffic that passes through it?
Item | Where it sits | What it does with traffic |
|---|---|---|
Router | Between two or more different networks | Reads the destination IP address and forwards the packet to the next hop chosen from its routing table (OSI Layer 3) |
Switch | Inside one LAN segment, between hosts | Reads the destination MAC address and forwards a known-unicast frame out of only the port learned for that address; frames for unknown or broadcast addresses are flooded to the other ports (OSI Layer 2) |
Hub | Inside one LAN segment, between hosts | Regenerates the incoming electrical signal and repeats it out of every other port (OSI Layer 1) |
CPU | On the motherboard inside one computer | Nothing — it fetches, decodes and executes that machine's own instructions and has no port, no address table and no link to another machine |
Cross-check — A quick way to confirm the classification is to ask what breaks when the item is removed. Take away the hub or the switch and the hosts on that LAN segment can no longer exchange frames; take away the router and traffic can no longer cross from one network to another. In each of those cases the machines themselves are still fully working computers — only the communication path between them is lost. Take away the CPU and that one computer cannot run at all, while every other machine on the network is unaffected — the loss is computational, not communicational.
Answer — CPU is the item in this list that is not a network device.