Old Xiaomi router devices can't connect to WiFi 6? WiFi 5 compatibility mode is a one-click emergency solution, but you have to calculate this before you start

last month, I dug out the old notebook I used for school in 2016, hoping to move it to my study as a machine for hanging up and downloading downloads. When you turn on the device and connect to WiFi, something strange happens: you can find the WiFi name, the password is correct, but after spinning around for a long time, a message pops up: "Cannot connect to this network." Occasionally, if you don't last more than ten minutes, you're likely to disconnect. This machine was working perfectly before the New Year at my mom's house, so why did it go on strike as soon as it arrived at my place?

spent the whole night messing around, and finally found a switch called 'WiFi 5 Compatibility Mode' in the 31.1 backend, which solved it in a minute. But this switch isn't for free—the whole house's speed has to be paid for. This article lays out the investigation process along with this account.

first identify which type of connection is missing, and don't rush to adjust the settings

the phrase "can't connect" actually hides two completely different diseases. Compare a piece of paper with

can't find the name, it's about frequency bands. I wrote the steps for dismantling the dual-band integration in the on separating 2.4G and 5G. You can check the actual band differences the from the actual test of the frequency bands, so I won't repeat it here.

my old model is the standard second type. There's a pretty cliché but a useful way to verify it: open a hotspot on your phone and let your old friend connect to it. If it connects on the first try, it means the network card and driver are not broken; the root cause lies in the process of "matching the password" with the router. If you can't even connect to the hotspot, that's your computer's own problem, not the router.

root problem: Old network cards can't understand the self-introduction of WiFi 6

router broadcasts its capability list every so often, and the WiFi6 router's list includes the item "ax." In recent years, network cards have seen AX and know it's new, so they shake hands as usual. But for the wireless network cards from 2013 to 2016, the Intel 7260 and 3160 generations, drivers stopped updating too early, so parsing this ax-labeled list would cause errors, and a mistake would result in a failed handshake.

this is not contradictory. The "backward compatibility" promoted by routers refers to compatibility after connection; The handshake window was too short, leaving no room for any mistakes in the analysis. So old equipment isn't 'slow to connect'—it's that it never got in.

figured this out, and the question of being fine at my mom's place before the New Year was solved: she used the WiFi that came with the optical modem, honestly WiFi 5, and there was no AX option in the broadcast. The old network card read smoothly. The first time I got to my house, I bumped into a WiFi 6 router, and that's when I got sick. IoT modules like vacuum cleaners and smart sockets fail to connect via the same mechanism. In my article about network configuration failure, I wrote about how a universal router can change the wireless mode from ax/ac/n hybrid to N only. However, Xiaomi's official firmware doesn't have a band mode option in the background. Scrolling through the settings page, it only gives a master switch.

Where is the

switch: Scroll down to the WiFi settings page

your browser and enter 192.168.31.1 to go to the backend, go to 'Frequently Used', click 'WiFi Settings', scroll to the bottom, and you'll find a subtle 'WiFi 5 Compatibility Mode'. Check it and save.

I want to explain the location of this switch in detail, because like DNS and manual channels, it doesn't exist in the Mijia app. It's a webpage backend feature. If you can't find it on your phone, don't doubt yourself. The official help document explains this switch as follows: Some older devices do not support WiFi 6 well. If scanning fails or connection fails, enabling this option will switch the router to WiFi 5 mode.

The moment

is saved, the whole family's WiFi disconnects once—any wireless settings change will do this, and it's normal. After reconnecting, my old account was back in one go, and I crashed all afternoon without disconnecting. The download tasks ran steadily.

But one thing must be clarified first: this switch is a one-size-fits-all approach for the entire house. There's no option to downgrade only one device; if enabled, all your family's WiFi devices will revert to WiFi 5.

one more remark: its relationship with dual-band integration is to avoid confusion: dual-band integration controls "whether 2.4G and 5G use the same name," compatibility mode controls "whether the broadcast has ax in the broadcast," and the two switches operate separately, neither affecting the other. Remove the dual-band and then enable compatibility mode, or just enable compatibility mode without changing the dual-band mode—either works according to your home needs.

After

is opened, the whole house is at a rate

my main router is AX3000T, which I've used for two years. It's a 2x2 machine running 160MHz, with a negotiated speed of 2402Mbps on WiFi 6 (I wrote about the base of this machine in my test in ). I enabled compatibility mode, dropped back to WiFi 5's 80MHz, and negotiated it dropped directly to 1201Mbps—on paper, it was cut in half.

actual measurements aren't as scary as they look on paper:

dropped by just over 10%. Why is the perception on foreign websites so low? Gigabit broadband plus gigabit Ethernet port, the ceiling is already 940, and the WiFi 5 1201 negotiated for over 500 yuan still can't reach the ceiling. The real headaches are the high-traffic Wi-Fi internal network—like using your phone to the NAS for wireless backup photo library or wireless screen casting to Blu-ray discs. These scenarios rely heavily on WiFi 6's high negotiation rate, and after downgrading, you can noticeably feel the slowdown.

sum up the whole account in one sentence: at home it's gigabit or below broadband, and daily I just watch videos and play games, so I basically don't notice anything when I turn it on; If you have 2000 Mbps broadband at home or frequently send large files wirelessly, it feels bad after a while.

an unexpected tip: the WiFi 6 router's 2.4G also comes with AX, and after enabling compatibility mode, the 2.4G is reverted to the previous generation. If you have a smart socket with ESP8266 old modules at home, the success rate of network installation will increase, essentially getting a layer of compatibility for free. On the other hand, if you ever want to turn off this switch, just tap save in the WiFi settings page. The whole family will disconnect and reconnect again. If you have many smart devices at home, just turn it off when no one is using the internet at night.

don't want to downgrade the whole house, there are still three options

compatibility mode is the easiest trick, but not the only one. Later, I made a round of trips and listed all the roads I could take:

first point: move old equipment to another network. I happen to have a ready-made one at home—an old AX3600 modified AP single-output 2.4G dedicated to feeding smart devices (how this topology works depends on the in the AP mode article; why choose this one depends on AX3600 ). Connect your old capital to that IoT private network, and the main router doesn't need to change a single character; the new device should run 2402 or 2402. The trade-off is that the network card is slow, the download machine can only run 60 to 70 Mbps, and some non-urgent things are enough for AFK use, but it can't handle urgent tasks. For families without a second router, just ignore this road.

second rule: add a USB wireless network card to your old bank. Plug in a small AX1800 network card for about 30 yuan, upgrade your old bank to WiFi 6, which is less hassle than fiddling with a router. I'll write about how to pick this part in the of the USB network card.

the third is to enable compatibility mode. If you have three or four old devices at home, you need to use them every day and connect immediately, so you can turn them on. Losing over 10% of the speed for the whole family is a worthwhile deal.

my own ending was a bit nonsensical: when renovating the study, I left a network port, then finally plugged in an Ethernet cable for my old laptop, maxed out over 900 Mbps, turned off compatibility mode, and restored WiFi 6 throughout the house. After fussing all night, the cheapest solution turned out to be just a single network cable.

open it under certain circumstances, and don't touch it under any circumstances

Let's go through the

troubleshooting sequence again: First, check if it can't be found or connect—if you can't find the frequency band or connect, check the network card with your phone's hotspot—confirm it's a generational issue, then decide whether to enable compatibility mode or bypass it. Don't rush to factory replacement; that would require a reconfiguration for the whole family.