Case Studies / Latest Case A 1000 Mbps Telstra Plan Testing Under 100 Mbps on a Cable: the One Printed CAT7 Was the Bottleneck (Adelaide)
Student · AdelaideTelstra 1000 MbpsFibre connectionNetcomm routerHouse · two switches80-minute remote video session
When this came in online it read like a straightforward speed complaint, the sort of thing that is usually one setting or one port. It was not. It took 80 minutes of remote video guidance, and the reason is that the house was wired throughout — two switches in different rooms and dozens of cables, any one of which could have been the weak link. The two that were had one thing in common: what was printed on the jacket did not match what the cable actually carried.
Where the speed was actually going
Wired test · before vs after
2cables replaced — the plan, the provider and the router all stayed the same.
The reported figures were the useful part: under 200 Mbps over WiFi standing right next to the router, and under 100 Mbps on a cable. On a 1000 Mbps plan both of those are wrong, but the wired number is the one that matters most, because a cable takes almost every variable out of the picture. If a wired test cannot clear 100 Mbps on a gigabit service, the problem is very unlikely to be WiFi coverage, walls or interference.
Why this took 80 minutes instead of 10
Four things stacked up, and they are worth naming because they apply to a lot of remote jobs.
- Nobody was on site. Every observation had to be described, framed on camera and confirmed, which costs time on each loop.
- Limited spare gear. With few known-good parts on hand, each test-and-verify cycle takes far longer than swapping a part and moving on.
- A complex environment. Two switches in different rooms and dozens of cables, so the number of candidate weak links was large.
- A house wired end to end. Devices talked to each other through cabling rather than WiFi, which is normally the good news — until the cabling itself is the thing that is wrong.
The student made the difference here: they drew the home network layout out by hand, and once there was a diagram to point at, the session stopped being a guessing game and became a list of segments to test in order.
The two cables
Two weak links on one wired house
Telstra fibre service
1000
→
Cable printed CAT5E
under spec
Bottleneck
→
→
Cable printed CAT7 between switches
under spec
Bottleneck
→
Devices on the far switch
slow
A wired house is a chain of cables, and a chain runs at the speed of its weakest link. Here there were two weak links in series, which is why replacing only one of them would not have looked like a fix. The second one is the nastier of the pair: the jacket said CAT7, which is a higher category than the job needed, and it still measured under spec — so it survived every visual check.
Step by step over video
An 80-minute remote session, step by step
1
Started from the reported numbers, not from guesses
WiFi under 200, wired under 100
2
Student drew the home network layout on paper
House wired via two switches
3
Worked the run from the NBN box to the router first
One cable printed CAT5E
4
Swapped that run to CAT6 and retested
Router speed up noticeably
5
Moved to the cable between the two switches
Printed CAT7, measured under spec
6
Replaced it with CAT6 and retested end to end
Wired and WiFi both up to plan
Printed category vs measured throughput
What the cable said vs what it delivered
| Printed on the jacket | What it measured | After swapping to CAT6 |
|---|
| NBN box → router | CAT5E | Under spec for the plan | Noticeable jump at the router |
| Switch → switch | CAT7 | Looked fine, tested under spec | Speed met the target |
| What changed | Nothing else in the house | Same plan, same router | 1000 Mbps plan met |
This is the part most people will not expect. A cable that is physically intact, plugged in firmly at both ends, with a category printed on it that is more than good enough for the job, can still be the reason a gigabit plan behaves like a 100 Mbps one. Nothing about it looks wrong. It only shows up when you test that one segment on its own, or swap it and watch the number move.
If you have a wired house and your speeds are short of what you pay for, the practical version of this case is: stop trusting the label, start testing segment by segment, and keep a couple of known-good CAT6 leads around to swap in. That is the whole method.
If you are troubleshooting this yourself
- Test on a cable first, right at the router. It removes WiFi from the equation and tells you whether you are chasing a coverage problem or a wiring one.
- Draw the layout. Boxes and lines on paper beat a verbal description every time, and it is what made this session workable at all.
- Change one thing at a time and retest immediately, so you know which change produced which number.
- Treat the printing on a cable as a claim, not a fact. The one marked CAT7 here was the slower of the two problems.
- Remote video guidance genuinely works for this class of problem when someone at the property can move cables and read numbers off a screen. We use it for addresses outside Sydney, and this Adelaide job is a fair example of what it can and cannot do.
Result
Two cables were replaced and nothing else in the house changed. The run from the NBN box to the router was printed CAT5E; swapping it to CAT6 lifted the speed at the router noticeably. The cable between the two switches was printed CAT7, looked perfectly fine and measured under spec; replacing it with CAT6 brought that segment up to target. Wireless and wired speeds both improved substantially, to what the Telstra 1000 Mbps plan should test at.