How to troubleshoot a Xiaomi router with slow internet speed? The gigabit dropped to just over 200. I investigated all night, and three of the real culprits were still stacked together

last Wednesday night at 8 p.m., the house felt like a collective strike: the TV was spinning in 4K, my wife's short videos were stuck at three seconds, and my mom's bedroom video calls were stuck as slideshows. My home has been using gigabit broadband for two years AX3000T (I wrote about two years of actual testing). In the living room, the phone can usually run 680Mbps on 5G, but that night I tested it at 230, sometimes fast, sometimes slow. My first reaction was that broadband in the area was out of control, almost costing 10,000. Then he thought it was better to investigate first. After two hours, there were three real culprits, and they were all stacked together. None of them were router failures.

Step

: Spend five minutes figuring out which segment is slow

slow internet is the biggest taboo when starting off or changing settings right away. My habit is to first plug the laptop into the network cable and test the speed via the router's LAN port. This step can easily eliminate most of the suspicions. If the computer reaches 935MB when plugged in, it means the broadband, modem, and router wires are all clean; the problem is locked in the wireless and device segments. I unplugged the same computer, sat in the living room, connected it to WiFi, and tested again. 230MB, sometimes fast, sometimes slow.

besides measuring which segment, you also need to distinguish "who's slow": slowing with the whole family or being slow with only one device are two different things, and the third line inside and outside the table is the hook left behind. If you're too lazy to turn on your computer, you can check the real-time speed of the entire broadband line in the Mijia app. A glance from the sofa to see if the uplink and downlink are fully loaded is just thirty seconds. If you only test with network cables at 100 or 200 Mbps, that's the broadband side's work: check light degradation, modem, carrier one by one. I've written four-layer check, so I won't repeat it here. There's also the speed test itself—turn off the background apps that steal data before testing, and which tool to use for accuracy—if you're wrong, you'll be blaming the router. read the speed test article before you act.

Culprit One: The upstream was all eaten by my mom's phone

the whole family gets stuck and the TV gets hit first, it's 90% of the time it's not the router's fault, it's the uplink issue. My home has gigabit broadband, 940Mbps downstream, and only 50Mbps upstream, which is enough for daily use. The problem is that one device can take over the entire internet. Why can upwards drag down downsides? When downloading, TCP must send back acknowledgments, but the return route is blocked, so download speeds still drop. I wrote about this in my speed testing article. When running 4K streams on TV, the confirmation packet is the most reliable, so it always spins in circles first. It looks like broadband is broken, but it's actually backhaul blockage.

opening 192.168.31.1, the homepage device list shows real-time speeds for every device. A quick glance shows a HUAWEI phone's upload speed at 5.5MB/s—converting to 44MB, it eats up nearly 90% of my 50MB uplink. I clicked it and saw it was my mom's. She stayed at my place for a week. That Huawei Cloud Gallery had Wi-Fi auto-sync enabled by default, and the phone had two years of photos and videos saved up. The sync queue was still 19GB, and running at full speed at 5.5MB/s would take over an hour, during which the whole family had to keep the SIM card company.

practice method is divided into two levels. For now, I set the phone's device-level speed limit, set the upload to 2MB, and keep the download unchanged. In 31.1, you can set it on the device detail page, and the speed limit article has a complete path . Within less than a minute of the time limit, the 4K TV stopped spinning, and the living room 5G went from 230 to 410 yuan. The long-term plan is on her phone: set → Huawei account → cloud space → gallery, turn off "gallery data synchronization," or switch to manual reconnection. Originally, she could have isolated her from the visitor network by one layer, but the elderly found switching back and forth annoying, so simply turning off sync was the easiest way. How do you usually catch those who steal traffic in your device list? the article on catching traffic is even more detailed .

Culprit 2: The nailed channel was squeezed by a neighbor's newly installed machine

finished repairing upstream, my mom's bedroom video still paused every few seconds, and the vacuum even disconnected once that night. Both symptoms point to 2.4G. I installed a WiFi Analyzer on my Android phone and scanned the area: my main router's 2.4G was already stuck on channel 1—before, the automatic channel jumped to 12 in the middle of the night, and the vacuum cleaner's cameras all lost contact once. then I manually pinned the —but my neighbor recently installed two new broadbands, and the router's automatic channel was all on channel 1, with three signal pillars stacked in one grid, making it hard for anyone to run smoothly.

2. 4G only has three channels that don't compete with each other. Fixing them doesn't mean it's a permanent solution. Neighbors have newly built PCs or changed routes, so the landscape changes at any time. On the 5G side, the channels basically don't overlap and can't be crowded; worrying about 2.4G is enough. Comparing the scan, 6 was the most empty that day, so I moved the main router to 6; The old AC2100 on the IoT private network sits on the 11, still staggered from the main router. Don't copy my numbers—which space is empty in your home? Look at your own scanned image from that day. By the way, my mom's bedroom is farthest from the main router, and her phone can only access 2.4G. If the channel is congested, she's the first to suffer. Rooms with weak signals can amplify the crowding—this is a false illusion of two faults stacked together.

the night I finished the modification, the bedroom video went smoothly, and the vacuum cleaner never disconnected again. For the channel issue, I recommend scanning it every quarter as a way to give the internet a check-up. checkup checklist I've written periodically.

True Culprit 3: The TV is installed by itself and the internet is slow

after repairing the first two parts, the 4K TV still spins twice. I almost thought it was the fourth issue. Going back to 31.1, the TV's real-time rate is nowhere near maximum, and the signal is still nice at -52. Later, I realized something was wrong—the TV menu was lagging, and opening the settings page took two seconds. This isn't a network issue; the TV system itself is lagging. Turn off the power for thirty seconds and then turn it on, then everything goes smoothly.

this TV hasn't been restarted for half a year. Smart TVs are just like smartphones—the more you use them, the fuller the memory, and when they lag, it feels like a slow internet. Therefore, checking network speed must be done in this step: distinguish whether it's "slow internet" or "slow device." The menu keeps spinning, so restart the device first—don't mess with the router. when I wrote about the TV networking , I also mentioned this classification: buffer is the network, screen interruption is decoding, menu cards are the system, and three types of lag are three types of issues.

three suspects casually dismissed

investigation, it's impossible for every suspect to be true. I casually missed three this round.

Riding the Firewall: The device list lists 66 devices. Each device opens to check the online time and MAC manufacturer, all of which are self-owned devices. Honestly, how to check how to check Riding on the Wikipedia has written . Number of devices built: 66 units, far from the AX3000T's rated 128 units. Memory usage is just over 60%, not at the bottleneck. 62 the 'Desktop Slimming' article have a benchmark number. Heating: Touched the casing, it's warm and not hot to the touch. compared to the gear I measured with a thermometer, 41°C is normal. There was also a free restart: my home restarted at 4 a.m. every Wednesday, and the automatic restart had just occurred on the morning of the incident, running for 16 hours, so it wasn't even considered a suspect.

half of the fun of checking is about eliminating it. If it feels hot to the touch, or if you have over a hundred devices, that's a different illness. the fever article have another treatment method.

the completed bill and the order in which it was copied

retest at noon the day after the repair, the living room 5G returned to 680, then tested 655 again at 9 PM during peak hours, and the drop below 10% is considered normal. Looking back, none of the three real culprits are fatal: the uplink gets 44 Mbps consumed, three channel pillars stacked per grid, and the TV memory card stacked together pushes gigabit down to 230. The trouble with slow screening is that's the problem. If you follow a single symptom, you'll always be one layer behind.

follow the sequence: plug in the computer with network cable and lock segments, see who uploads the 31.1 device list to see who can handle it, scan images to change channels, restart the device that rebooted the card itself, and scan again next quarter. If the router isn't broken, don't try to restore it to the factory. My unit restarts every Wednesday at 4 a.m., and it's still stable for two years. Here's another foolproof habit: when guests come to stay long-term or add new equipment, just glance at the uploaded list the day before and guess a night earlier than afterward. The slower web is almost always the result of stacking up layers, layer by layer, much faster than guessing.