Ethernet link / about 5 minutes
Symptom: slow downloads. Check: adapter link rate showed 100/100 Mbps. Fix: replace the Ethernet cable. Validation: download performance recovered after the replacement.
01 / IT support / troubleshooting
Three small IT problems, isolated quickly
Three real freelance support requests: a 100 Mbps Ethernet link, a no-boot memory change, and a DNS resolution failure.
Starting point
Where it started
Each person knew only that something was slow or broken. I needed to translate the symptom into a likely layer, make one focused change, and confirm the original problem was gone.
What I did
What I worked on
- Found an Ethernet adapter negotiating at 100/100 Mbps, recommended replacing the cable, and confirmed the faster link after the swap in about five minutes.
- Helped recover a PC that stopped booting after a memory change by correcting the DIMM seating and slot placement in about one minute.
- Isolated a browsing problem to DNS resolution, changed the device to Cloudflare DNS, and confirmed name lookups worked in about five minutes.
- Explained what failed and why each focused change was safer than changing several settings at once.
Evidence
What I checked and recorded
Memory no-boot / about 1 minute
Symptom: PC stopped booting after RAM was moved. Check: module seating and motherboard slot layout. Fix: reseat the modules in a supported paired layout. Validation: the system completed startup.
DNS resolution / about 5 minutes
Symptom: searches and named sites failed. Check: separated name resolution from basic connectivity. Fix: set Cloudflare as the resolver. Validation: domain lookups and browsing worked again.
Result
What changed
All three systems returned to normal in five minutes or less, and each person left knowing which component or setting caused the symptom.
What I learned
What I took from it
- Link speed is evidence, not just a number in a settings panel.
- After a hardware change, check seating and the board layout before assuming a failed part.
- A DNS failure can look like the internet is down even when the connection itself still works.
Next case study / 02