Network Design for a Portable Classroom
A school adds a portable classroom 60 m from the main building. It needs 30 student devices, one teacher laptop and a networked printer. The main building has a fibre connection and a switch with spare ports. The portable has no cabling. The school's Wi-Fi in the main building already suffers interference at lunchtime. The business manager proposes a single long Ethernet cable from the main switch to a cheap unmanaged switch in the portable, with one Wi-Fi access point. The IT teacher is asked to review the plan before purchase.
1. Evaluate the proposed cabling and switching plan. Identify the main technical risks and recommend improvements.
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A single Ethernet run is fine in principle but 60 m exceeds typical 90 m channel limits only if the total path (including patch leads and bends) exceeds 100 m; at 60 m it is within limits, so the run itself is acceptable if installed properly (conduit, no sharp bends, no mains interference).
Risks: (1) no redundancy, so one cable fault takes the whole portable offline; (2) an unmanaged switch gives no VLANs, no port security and no monitoring; (3) one access point for 30 devices plus interference at lunchtime will hurt throughput; (4) no UPS or surge protection on the long run.
Improve: use a managed switch with VLANs separating staff, students and printer; run two cables (or a fibre link with media converters) for redundancy; add a second access point or use 5 GHz channels to reduce interference; label and test the run.
2. The printer must be reachable by teacher and student devices but not by the wider school network. Explain how to achieve this.
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Put the printer on its own VLAN in the portable, with the managed switch routing only between the student and teacher VLANs and the printer VLAN. Apply ACLs so only those two VLANs can reach the printer's IP on the print ports, and block the printer from initiating connections outward. The main building's router should not advertise a route to the printer VLAN, so the wider network cannot reach it.
This gives least privilege: the printer is usable where needed, isolated elsewhere, and cannot be used as a pivot if compromised. The IT teacher should document the ACL rules and test from both an allowed and a disallowed device.
3. Lunchtime Wi-Fi interference is already a problem. Recommend a change and justify it with reasoning about the 30 devices.
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30 devices on one access point is heavy, especially if many stream video at once. Interference at lunchtime suggests channel overlap or too many clients on 2.4 GHz. Recommend dual-band access points, force 5 GHz where possible, set non-overlapping channels (e.g. 1, 6, 11 on 2.4 GHz; distinct 5 GHz channels), and cap the number of clients per AP.
Justification: 5 GHz has more channels and less congestion, so 30 devices spread across two APs is far more manageable. The school should also apply a per-device bandwidth limit at lunchtime so one device cannot starve others. Measure before and after rather than assuming the fix worked.