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✍ 02: Infrastructure & Documentation — Exercises

Network Systems

Module 02: Infrastructure and Documentation 12 questions

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🔌 Q1. Order these structured-cabling elements from the user's desk out to the ISP: MDF, work area, demarc, IDF, entrance facility, horizontal cabling, backbone cabling.

Show answer **Work area → Horizontal cabling → IDF → Backbone cabling → MDF → Entrance facility → Demarc** (→ ISP).

🔌 Q2. What standard defines structured cabling for commercial buildings, and what topology does it assume?

Show answer **ANSI/TIA-568**, which assumes a hierarchical **star** topology.

💡 Q3. A horizontal copper run measures 92 m of solid-core plus 12 m of patch cords. Does it comply with TIA-568? Why?

Show answer **No.** Total channel = 92 + 12 = **104 m**, exceeding the **100 m** limit (≈90 m permanent link + ≈10 m patch cords).

🔹 Q4. You must connect two switches on gear without Auto-MDIX. What cable type do you need, and which pin standards go on each end?

Show answer A **crossover cable** — **T568A on one end, T568B on the other**. (With Auto-MDIX, a straight-through would also work.)

❓ Q5. What is the difference between the MDF and an IDF?

Show answer - **MDF (Main Distribution Frame)** — the central point of the building's cabling; houses core routers/switches and the main cross-connect. - **IDF (Intermediate Distribution Frame)** — a smaller wiring closet (often per floor) that aggregates work-area cabling and links back to the MDF via backbone cabling.

🧱 Q6. A rack holds a 1U firewall, a 2U server, and a 4U UPS. How many rack units are used, and where is this recorded?

Show answer 1U + 2U + 4U = **7U** used (1U = 1.75 in). Recorded in a **rack elevation / rack diagram** showing each device's starting U position.

❓ Q7. What is the demarcation point (demarc)?

Show answer The boundary where the **service provider's** responsibility ends and the **customer's** begins — useful for pinpointing who owns a fault.

🔹 Q8. Distinguish a physical network diagram from a logical network diagram, with one item each would contain.

Show answer - **Physical** — actual devices, ports, cable runs, locations (e.g., "Switch A port 12 → Room 204 jack"). - **Logical** — IP addressing, subnets/VLANs, routing, data flow (e.g., "VLAN 10 = 192.168.10.0/24").

❓ Q9. What is a performance baseline, and why is it valuable?

Show answer A record of **normal** traffic, utilization, latency, and error rates. It lets you recognize anomalies (spikes, slowdowns, breaches) by comparison and supports capacity planning.

🔹 Q10. List the minimum contents of a change request for replacing a core switch.

Show answer Reason/scope, risk assessment, implementation plan + maintenance window, **rollback (back-out) plan**, and **approval/sign-off**. (Never personal credentials.)

🔹 Q11. What do the metrics MTBF and MTTR measure?

Show answer - **MTBF (Mean Time Between Failures)** — average operating time before a device fails (reliability). - **MTTR (Mean Time To Repair)** — average time to restore a failed device/service (recovery speed).

💡 Q12. Where must plenum-rated (CMP) cable be used, and why?

Show answer In **air-handling spaces (HVAC plenums)**. Plenum cable uses fire-resistant jacketing that emits **less toxic smoke** when burning, meeting fire code where building air circulates.

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