I recently moved out and signed up for a 1 Gbps fibre broadband plan, but speed tests show about 120 Mbps download and 98 Mbps upload. My PC is connected by Ethernet using a Cat 5e cable to a TP-Link device mounted on the wall, which is connected to my router with a Cat 7 cable. I'm new to networking, so I'm not sure whether the problem is the cables, the TP-Link equipment, the router, or the way I'm testing the connection. What should I check first?
4 Answers
First, check the units. Internet speed tests normally use megabits per second, written as Mbps. If you’re looking at a download rate of 120 megabytes per second in an app, that’s roughly 960 megabits per second—almost the full gigabit. Make sure the test is showing Mbps, not MB/s.
Cat 5e should handle a 1 Gbps connection over normal home cable lengths, so the cable type probably isn’t the issue. Temporarily connect the PC directly to a gigabit LAN port on the router and run a test on a reputable speed-test site. Turn off Wi-Fi on the PC while testing and try more than one nearby test server.
The TP-Link device needs to be identified— it could be a switch, access point, powerline adapter, or another router, and some of those can be the bottleneck. Check the model numbers and verify that the PC’s Ethernet link shows 1000/1000 Mbps rather than 100/100 Mbps. Also make sure the cable is plugged into a LAN port rated for gigabit speeds.
If the direct router test is still around 120 Mbps, check the router’s negotiated WAN and LAN speeds and confirm there isn’t a bandwidth limit, traffic-control setting, or outdated network driver. If the direct test reaches around 900–950 Mbps, reconnect the TP-Link equipment and test each link separately to find where the speed drops.

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