The Chromebook Cart That Drops Every Third Period
A portable classroom has 32 student Chromebooks and one teacher laptop. The only network access is a consumer-grade wireless router mounted at the front of the room, configured for 2.4 GHz channel 6, WPA2, and a DHCP pool of 40 addresses with 24-hour leases. The router is rated for 25 simultaneous clients. Three nearby classrooms use channels 1 and 11. A microwave in the teachers' lounge is 8 meters away through a wood-frame wall. During third period, 30 students simultaneously open a browser-based circuit simulator that loads 15 MB of assets. Symptoms: some Chromebooks show 'connected, no internet,' others load the simulator slowly, and the teacher's laptop loses connection when the microwave runs. The school's network administrator says the wired network is fine and the router's WAN link is 100 Mbps. The teacher has a spare 5 GHz access point but must submit a change request 48 hours in advance. Third period is in two days.
1. Distinguish among the likely causes of the three symptoms. Which symptom points to DHCP, which to RF interference, and which to client capacity or bandwidth?
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The DHCP pool has 40 addresses and the room has at most 33 devices, so simple pool exhaustion is unlikely unless old leases from other carts are still active. The 'connected, no internet' symptom is more consistent with the router's 25-client limit or NAT table exhaustion, because 30 students plus the teacher exceed the rated 25 simultaneous clients. Those extra devices may associate with the radio but fail to obtain usable forwarding. The slow simulator load is a bandwidth and airtime problem: 30 × 15 MB = 450 MB. At 100 Mbps, the raw transfer is about 36 seconds, but 2.4 GHz is shared, retransmissions increase with 30 clients, and the access point becomes the bottleneck, not the WAN link. The teacher's laptop dropping only when the microwave runs is classic 2.4 GHz interference: microwave leakage is near 2.45 GHz, and channel 6 overlaps that range. Neighbors on channels 1 and 11 are non-overlapping with each other, so co-channel interference from them is not the main issue.
2. Propose a diagnostic sequence using tools available on Chromebooks and the router, and the first change you would request. Justify why you would not simply buy a bigger internet plan.
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Diagnostics: on a Chromebook, use crosh to ping the default gateway, ping a public IP, and nslookup a hostname; this separates local Wi-Fi, routing, and DNS failures. Check chrome://net-internals for connection and DNS details. On the router, inspect the DHCP client list, active lease count, connected-client count, channel utilization, and logs. Repeat the teacher-laptop test with the microwave off and on. Compare a single-device speed test with a 30-device class test.
The first change to request is a 5 GHz access point with a higher client limit, with a separate SSID for the Chromebooks. 5 GHz avoids the microwave and channel 6 congestion and can provide more capacity, but the request must be checked against the spare AP's actual client rating. A bigger internet plan would not help because the WAN link is already 100 Mbps and the failure is at the wireless client and airtime layer. Submit the 48-hour change request immediately, and in parallel prepare the temporary workaround.
3. What temporary classroom workaround could reduce load during third period without compromising the lesson's learning objective? Explain the trade-off.
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Stagger the simulator launch. Half the class starts the simulator while the other half completes a paper truth-table or circuit-design task, then swap after 12–15 minutes. Alternatively, pre-cache the simulator on a few devices before class and have students work in pairs on those devices. Both reduce the number of simultaneous 15 MB asset downloads and keep the class under the router's practical client limit. The learning objective is preserved because every student still analyzes and tests circuits; only the timing and grouping change.
The trade-off is instructional time and individual hands-on minutes: staggering adds transition time and may reduce each student's direct device time. Pairing can hide one student's confusion unless the teacher checks both partners' work. Avoid disabling WPA2 or opening the network as a quick fix, because that trades a performance problem for a security and privacy problem. Document the workaround and its results so the change request can be justified with evidence.