How much can you trust the capacity of the router? A machine with a nominal 128 units ran into trouble when I installed 62 units. The location of the card was different from what was written on the details page.
The router at home is an AX3000T with a nominal capacity of 128. Last year, the number of smart devices was increased to 62. The sweeper disconnected in the middle of the night, the camera offline push was delayed, and the mobile phone connected to the Internet was normal. At first I thought the router was broken and almost ordered a replacement. Then I dug out two old routers and did a comparative experiment, and I figured out one thing.: The measurement method and usage of this number are different from what the details page wants you to believe. . This article lays out the entire experiment and the ledger. If you have a lot of equipment at home, you can check it yourself.
Make it clear first: What environment does the nominal belt machine measure?
The "supports 128 devices" number on the details page is not a liar, but it is a laboratory number. The manufacturer tested it under ideal conditions.: A single device, a single connection, almost no data transmission, just count the number of rows that can be registered in the router's ledger. This is more like the hotel saying "it can accommodate 128 guests" - it only counts beds, not whether there is enough hot water for everyone to take a shower at the same time.
In a real home network, devices cannot be registered quietly and then be finished. The camera pushes a stream every few seconds, the sensor wakes up every hour to report the temperature, and the sweeper transmits the map in real time when it is running. The router needs to record the address, connection, and WiFi transmission sequence for each device. These accounts all require memory and computing power. The number of devices is just an appearance. The pressure is calculated by multiplying the three numbers "number of units × number of connections per unit × flow rate of each unit" .
Therefore, 62 smart homes and 62 mobile phones and tablets are two completely different pressures. Of the 62 devices in my home, 45 are small devices such as sensors and cameras, and only 7 are used by real heavy traffic users. If you directly calculate "I have 62 units, the nominal number is 128, so why worry about half", the calculation will be wrong - that's how I was wrong.
My actual measurement: From 30 units to 62 units, all stuck locations are recorded
The number of devices on my router is slowly increasing, and it happens to be a ready-made pressure curve. I retrieved a few key nodes and corrected them.:
| Number of devices | Problems that arise | I thought it was | Practical reasons |
|---|---|---|---|
| 30 sets up and down | No feeling at all | — | The memory level is low and the ledger is more than enough. |
| Early 40s | Some cameras go offline in the middle of the night and come back on their own | Camera quality issues | The 2.4G channel becomes congested and retransmissions crowd out the line. |
| Over 50 units | The router opens slowly in the background. Change the settings and go around. | Browser convulsions | More than half of the memory is occupied, and the background response is laggy |
| 62 units | The sweepers collectively lost contact in the middle of the night, and the entire Mi family was lost. | The router needs to be replaced | The number of concurrent connections and 2.4G are both tight |
Looking back at this table, the most interesting thing is that: Every step I took was attributed to the mistake. . The life of the device that caused the camera to go offline, the browser that caused lag in the background, and finally the entire router that lost contact are actually three scales on the same pressure curve. If the router had been replaced at that time, and the machine was replaced with a nominal number of 256, more than 100 devices would still be stuck in the same position again.
By the way, "Old equipment drags down the whole family" is also part of this curve: Several old devices at home that only support 2.4G occupy far more air time than their traffic share. I am accounting for this. The article about old devices slowing down WiFi Counted separately, it’s worth looking at homes with a lot of devices.
Where does the stress come from?: Look at the three accounts one by one
When you take the router apart, you will see that as there are more devices, the pressure falls on three places. The order of importance is counter-intuitive. I will put the most ignored ones last.
The first one is the internal ledger. The router records a file line for each online device: MAC address, IP, connection status, traffic statistics, dozens of devices may not sound like much, but each device still drags connection records. I turned to the system status page in the background of the router. When there are 62 devices, the memory usage is around 70% all year round, and when there are 30 devices, the memory usage is just over 40%. When the memory is tight, the first thing to sacrifice is the background response speed and buffering capacity. What are the differences between machines with different internal archive locations? I am How much memory is enough? I have actually tested three machines, and concluded that you should be wary of 128MB machines and 40 devices.
The second one is the concurrent connection account. The number of units and the number of connections are two orders of magnitude: An idle mobile phone can occupy several connections, a mobile phone with cloud synchronization turned on can occupy two to three hundred connections, and a device connected to BT can occupy thousands. There is a NAT session table in the router to manage these connections. If the table is full, new connections cannot be established. The performance is "WeChat can be received, but no web pages can be opened." The night I signed up for BT insurance, I had a full meter. It has nothing to do with the number of devices. A single device can hit the full meter. What kind of information is this table full of and how to check it? Write it in The article about number of connections Here, families with many devices are recommended to know this troubleshooting idea, unlike me who restarted the router three times.
The third and most hidden one: 2.4G air time account. The first two books are in the belly of the router and can be seen. ； This one is in the air and cannot be seen. Only one device can talk in the 2.4G frequency band at the same time, and who knows how long it will take depends on the queue. Almost all smart homes are crowded on 2.4G. Even if the traffic of 45 small devices is very small, the frequent "wake up and say something before going to sleep" still fills the queue. OFDMA of WiFi6 has changed this queuing rule. Small devices can share rides and send packets. I am OFDMA article The queuing principle has been dismantled in this article - for families that get stuck when there are too many devices, it is worth confirming whether this switch is turned on or not.
Where is the red line for the number of units drawn?: Give me a number that can be implemented
After actual testing, my conclusion is that don’t use the nominal number divided by two as the safety line, use the machine configuration and equipment composition to estimate:
| Machine grade | Memory | Smart home-based families | Households dominated by mobile phones and tablets |
|---|---|---|---|
| Entry-level old model | Within 128MB | Be alert up and down the 25 platform | 15 units alert |
| Mainstream WiFi6 | 256MB | Be alert up and down the 50 platforms | 30 units alert |
| High-end/soft routing | 512MB or more | Basically stable within 100 units | 50 units and up |
The word "vigilance" on the surface does not mean "reporting an error", but it means that it is worth checking the water level every month. Why are smart home-based lines so high?: Sensor traffic is small, connections are few, and most of them occupy 2.4G queuing slots. ； Mobile phones and tablets have large traffic and cloud synchronization connections, which occupy session tables and memory. The locations of explosions in the two types of families are different.
There is also a variable that can increase the strength without spending a penny.: The OFDMA and MU-MIMO of WiFi6 can really reduce the burden in scenarios with many small devices. The old WiFi5 machine can carry 40 units, but a new WiFi6 machine worth 200 yuan may be able to carry 60 units. First make sure all the switches on your machine are turned on before talking about changing the machine.
How to check the real water level of your router
Three steps, five minutes:
The first step is to count the equipment. Log in to the router's backend and pull up the list of online devices, counting the total number. Don’t just count mobile phones and computers, but also include sweepers, cameras, door locks, and speakers. In many households, the number of real online devices is twice the “perceived number.” I was stunned that night when I counted 62 devices. How do I identify a bunch of unrecognizable device names in the background list one by one? I am The article about identifying equipment I have written about local methods.
The second step is to look at the memory. Check the memory usage in the system status or device management page. If the idle period during the day is above 60% all year round, this water level will most likely be even worse during the evening peak, which is a signal that “it’s time to plan.”
The third step is to monitor symptoms. If two of the three signals appear, it basically means the water level has reached: Smart homes are collectively disconnected in the middle of the night (2.4G is crowded), the router is turned on in the background and spinning (memory is tight), and the web page is open and closed but WeChat is normal (session table is tight). Three signals correspond to three accounts. Please turn to the previous paragraphs accordingly.
If it exceeds the standard, who will be killed first?: Four tips for not changing machines
The water level has really arrived, don’t rush to spend money yet, the four tips are ranked according to cost-effectiveness:
Make a new home for your smart home. If you have a second old router at home, move the entire smart home router to it: The old machine was set up to send only 2.4G and a separate SSID, and the main router was dedicated to serving mobile phones and computers. I did this during the experiment. The water level of the main router dropped directly from 70% to 45%, and the sweeper never lost contact in the middle of the night. How to connect two machines using a network cable, and whether the second machine should be used as an AP or as a router? I am here The article about wired connection between two routers The connection method is written here.
Reduce the load on the equipment side. Downgrade the most frequently used device to "wake up and say something": The camera's motion detection sensitivity is lowered by one level, and the sensor's reporting interval is reduced from a few minutes to more than ten minutes. The change of a single unit is small, but the stacking of forty units is a considerable burden reduction.
Eliminate the big players who eat connections. Use the connection number ranking in the background to find out the device that occupies the most session table. Most of them are mobile phones with cloud synchronization or old-fashioned download machines. Give it a speed limit or peak shift, and the session schedule will be relaxed immediately.
Change the machine last. If it's still tight after the first three moves, change it again. When replacing, don’t just look at the machine specifications. Pay attention to the memory capacity and whether there is OFDMA. How to translate the details page parameters into human language? I’m here When buying a router, read the parameters I sorted out the five elements and copied them directly.
ending: A self-examination sequence
Compress this article into an executable paragraph: Log in to the background first and count the actual number of devices (including all small devices) → Check whether the memory usage exceeds 60% all year round → Check the three accounts for disconnection symptoms that appear → If it exceeds the standard, try the three methods of moving the device, reducing the frequency, and limiting the number of large users → After all is done, consider changing the device. When changing the device, you can’t see the same “256 units supported” when looking at the memory and OFDMA. Just measure that number with a machine and treat it as a bed table. Whether the hot water for bathing in your home is enough depends on the water tank.
