Why is my Ethernet connection slower than my internet plan?
Usually the cable is not the limit. Test one computer plugged straight into the modem, with everything else idle. If that is fast, the router, a switch, an old port or a bad cable run is holding it back. If it is slow too, the problem is the plan, the provider's network or the modem, and the provider has to fix it.
Free to ask. Local shops send quotes, and you pay only when you book one.
By Kasra Taheri, Founder, LoclisPublished
Researched and drafted with AI, then checked claim by claim against the sources listed below before it was published. Prices and rules change; the dates beside each source say when it was last checked.
Step by step
Read when to stop and call a pro, further down this page, before you start.
Step 1: Pause everything else
Pause downloads, streaming and cloud backups on every device so the test measures the connection alone.
Step 2: Test straight at the modem
Plug a computer into the modem or fibre box with a short cable, skipping the router and wall jacks, and run a speed test.
Step 3: Compare with the plan
Compare the result with the speed on your bill, allowing for the provider's wording of what is typical or "up to".
Step 4: Test through the router
Plug the same short cable into a router port and test again. A big drop points at the router.
Step 5: Test through the wall jack
Connect the computer at the wall jack with a short patch cable and test again. A drop here points at the in-wall run or the switch at its far end.
Step 6: Check the link speed
Open the computer's network settings and read the Ethernet link speed. 100 Mbps on a gigabit plan means something in the path is limited to 100 Mbps.
Step 7: Swap the patch cables
Replace the short cables at each end with ones labelled Cat 6 or better and look at the link speed again.
Step 8: Restart and update
Restart the modem and router, install any pending firmware update, and try another router port or switch port.
Find which link is slow
Start by finding out where the speed disappears. A computer cabled straight into the modem shows what the provider is delivering. Every later test adds one piece of your own wiring, so the drop tells you which piece is at fault. The steps above do exactly that.
Run each test the same way: one device, nothing else using the connection, the same test site, a couple of runs. Speed tests wobble, so trust a pattern over one number.
If the modem test is slow too
Then the house wiring is not the cause. Plan speeds are what the provider sells, and what you get depends on its network. For cable internet, "Transmission speeds vary depending on the type of cable modem, cable network and traffic load."[1] For fibre, the FCC says "The actual speed you experience, however, will vary depending upon a variety of factors, such as how close to your computer the service provider brings the fiber and how the service provider configures the service."[1]
Run the test at a few times of day and write down the results. Check that your modem is rated for your plan, since an older one can cap a newer plan. Then call the provider with your results in hand.
If the modem test is fast and the wall jack is slow
Here the house is the bottleneck, and the usual causes are cheap to find:
- A 100 Mbps link. Every Ethernet link settles on the fastest speed both ends and the cable between them can manage. One weak part drops the whole link to 100 Mbps, even though cable made for gigabit lists both 1000BASE-T and 100BASE-T among its applications.[3] That is the classic cause of a gigabit plan reading 90-something Mbps.
- A 10/100 switch or router. Older equipment has 100 Mbps ports. Look for "10/100" on the label.
- An old or damaged patch cable. Flat, kinked or crushed cables lose pairs. Swap them first, because it costs the least.
- A poorly made in-wall run. Sharp bends, stapled cable, jacks wired badly or cable spliced with a coupler can leave you stuck at 100 Mbps or with errors. See how to run Ethernet cable through walls for how a clean run is laid out.
- The router or computer. A router that cannot route at gigabit speeds, or a computer with an old network adapter, shows up when a fast cable is plugged into it.
Is your plan the problem
Sometimes the connection is fine and the plan is simply smaller than you assumed. The FCC's Broadband Speed Guide lists 25 Mbps as the minimum download speed for streaming Ultra HD 4K video,[2] and its figures assume one activity at a time. A household streaming, gaming and video calling together adds those up, and a speed test run during all that will look low.
Keep the cable out of the blame
Cable is rarely at fault on its own. Siemon lists 10GBASE-T, 1000BASE-T, 100BASE-T and 10BASE-T among the applications its Category 6A cable supports, over a channel of up to 100 metres.[3] A cable of that grade carries gigabit across a house. When a wired link is slow, the culprit is almost always a port, a patch cable or a termination.
Stop and call a pro if
- Only some wall jacks are slow. The run to those jacks is probably poorly terminated or damaged inside the wall. A low-voltage installer can test and re-terminate it. See whether to hire a low-voltage contractor.
- Fixing it would mean opening walls or ceilings. Do not cut into framing or fire-rated construction on a hunch. Test first, then decide.
- The modem test is slow and the provider says everything is fine. Ask for a technician visit. The line, the outside wiring and the box at the home are theirs to check.
- A cable is near household power wiring and you cannot see how it is routed. Do not open boxes that hold line-voltage wires. Call a licensed electrician.
Getting help in Virginia
If you want the whole house cabled properly, read what wiring a house for Ethernet costs in Virginia. Browse Security & Smart Home or see more smart home answers.
When you are ready for tests and fixes done on site, describe the job once and local pros quote it.
Common questions
- Is Ethernet always faster than Wi-Fi?
- Not automatically, but it is usually steadier. A wired link avoids radio interference and distance, so it should reach what the plan delivers. If a wired test is slower than Wi-Fi, suspect the cable, the port or the link speed rather than the internet service.
- Which Ethernet cable do I need for a gigabit plan?
- Cat 6 or Cat 6A cable is made for gigabit and faster. Siemon, for one, rates its Cat 6A cable for 1000BASE-T and 10GBASE-T over a channel of up to 100 metres, which is longer than almost any run inside a house.[^siemon] The jacks, patch cables and switch ports along the route must also be gigabit.
- Why does my speed test show less than the plan?
- Delivered speed can differ from the plan. The FCC notes that cable modem speeds vary with the cable network and traffic load, and that fibre speeds vary with how the provider configures the service.[^fcc-qa] Test at the modem and at different hours to see which it is.
- How much speed do I actually need?
- Less than most plans offer for a single activity. The FCC's guide puts Ultra HD 4K streaming at 25 Mbps and HD video conferencing at 6 Mbps, but it counts one activity at a time, so a busy household needs the total.[^fcc-speed]
- Does a switch slow Ethernet down?
- A gigabit switch does not noticeably slow a gigabit plan. An older 10/100 switch does: every device behind it is capped at 100 Mbps. Check the label on any switch hidden in a closet or behind a wall plate.
Sources
- [1] Getting Broadband Q&A, Federal Communications Commission. Checked October 27, 2026.
- [2] Broadband Speed Guide, Federal Communications Commission. Checked October 27, 2026.
- [3] Spec Sheet, Category 6A F/UTP 4-Pair Cable, Siemon. Checked October 27, 2026.
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