✍ 01: Introduction to Networking — Exercises¶
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🔹 Q1. List the seven OSI layers in order (Layer 1 → Layer 7).¶
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1. Physical 2. Data Link 3. Network 4. Transport 5. Session 6. Presentation 7. Application Mnemonic (1→7): *Please Do Not Throw Sausage Pizza Away.*❓ Q2. What is the Protocol Data Unit (PDU) name at the Data Link, Network, and Transport layers?¶
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- **Data Link (L2)** → **Frame** - **Network (L3)** → **Packet** - **Transport (L4)** → **Segment** (TCP) / datagram (UDP) Full sequence down the stack: Data → Segment → Packet → Frame → Bits.🔹 Q3. Classify each device by the OSI layer it primarily operates at: hub, switch, router, NIC.¶
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- **Hub → Layer 1** (repeats signals out all ports) - **NIC → Layers 1–2** (physical connection + MAC address) - **Switch → Layer 2** (forwards frames by MAC) - **Router → Layer 3** (forwards packets by IP)❓ Q4. What is the difference between a collision domain and a broadcast domain? Which device breaks up each?¶
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- **Collision domain** — a segment where frames can collide. **Switches** break these up (one collision domain per port). - **Broadcast domain** — the set of devices a broadcast reaches. **Routers** (and VLANs) break these up.📁 Q5. A 6-computer office shares files directly with no server; a 300-user firm uses central logins. Name each network model and one advantage of each.¶
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- Small office → **peer-to-peer** — cheap, simple, no server/NOS required. - 300-user firm → **client-server** — centralized authentication, backups, and control; scales well.🌍 Q6. Match each scope to its example: PAN, LAN, MAN, WAN — (a) the Internet, (b) a Bluetooth headset, (c) an office network, (d) a city-wide fiber ring.¶
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- (a) Internet → **WAN** - (b) Bluetooth headset → **PAN** - (c) office network → **LAN** - (d) city-wide fiber ring → **MAN**🔍 Q7. A user reports "the Internet is down." Apply the first three steps of the CompTIA 7-step troubleshooting model.¶
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1. **Identify the problem** — ask what "down" means (all sites or one app?), what changed, when it started, who's affected. 2. **Establish a theory of probable cause** — e.g., DNS failure, gateway down, or ISP outage; question the obvious (cable, Wi-Fi). 3. **Test the theory** — `ping 8.8.8.8` (tests connectivity) then `nslookup` (tests DNS) to confirm or refute.🔍 Q8. What are the last two steps of the 7-step troubleshooting model?¶
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- Step 6: **Verify full system functionality** (and implement preventive measures). - Step 7: **Document findings, actions, and outcomes.**💡 Q9. Which OSI layer would you check first if the link light is off and the cable seems dead? Why?¶
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**Layer 1 (Physical)** — cabling, connectors, and port/link status are physical issues. Higher layers can't function without a working physical link, so bottom-up troubleshooting starts here.🔹 Q10. What safety device prevents static electricity from damaging components, and what document lists safe handling of hazardous materials?¶
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- **ESD (anti-static) strap** — bleeds static charge from your body to prevent electrostatic discharge damage. - **MSDS / SDS** (Material/Safety Data Sheet) — handling, storage, and disposal info for hazardous materials.🔹 Q11. In a physical star topology, what happens if one workstation's cable breaks vs. if the central switch fails?¶
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- One cable break → **only that one node** loses connectivity. - Central switch failure → **the whole star** goes down (the switch is a single point of failure). This is why star is easy to manage but the central device should be made redundant in critical designs.🔹 Q12. Give one advantage and one disadvantage of a full-mesh topology.¶
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- **Advantage:** maximum redundancy — every node has a direct link to every other, so a single link failure doesn't isolate anyone. - **Disadvantage:** cost/complexity — the number of links grows rapidly (n(n−1)/2), so it's expensive to build and maintain.📚 All Exercises · Next: Module 02 — Infrastructure & Documentation ➡️