Recently, the 2.4GHz band Wi-Fi at home was quite unstable, and I had a problem with it. increase.
It's hard to realize that your Wi-Fi will collapse just by plugging it into an outlet upside down, right?
Only some Wi-Fi devices are unstable
This does not mean that all Wi-Fi devices in your home are bad. . (Unstable as it goes up)
The specific symptom is that the Wi-Fi disconnects and connects. In other words, depending on the situation, the communication could or could not go through.
This symptom, especially after changing the AP connected to Echo Show 5 from 5GHz to 2.4GHz band, was really bad, and my home's smart home function almost collapsed.
What is interesting is that the MacBook Air, Windows PC, iPhone, and Android connected to the same Wi-Fi router's 5GHz band SSID do not show any symptoms, and the cleaning robot "Rumba" can only use the 2.4GHz band. And "Braba" is also no problem.
I had the impression that the symptoms were caused by a cheap and small device that seemed to be poorly made.
The cause is the polarity of TP-Link's smart plug "HS105"
There is no point in complaining, so we first investigate the cause.
However, it is a tough environment with a wife who is working remotely. My wife absolutely hates collaborating with other people, and she refuses to make any adjustments as to when it is okay to do network maintenance work. From morning to midnight, from weekdays to weekends and holidays, taking into account my schedule, they don't give me the timing to stop the network in units of half a day.
While stricter restrictions are imposed than a small workplace, we will proceed with the investigation of the home network.
First, I used a Wi-Fi analyzer to observe the channels used by the surrounding 2.4GHz band SSID, which was probably as large as a school of fish.
Lots of fucking APs out of 1, 6, 11ch golden channels. The output is too high. Multiple radio waves of -50dbm or more are flying from outside, what is this? Are you beamforming from your neighbor's window to your house? While thinking about such things, for the time being, I understand that it seems like I'm going to interfere. terrible situation.
So, while stealing my wife's attention, I tried various settings that seemed to increase the reliability of Wi-Fi in a congested environment.
A few months later, a turning point came.
However, an error like "Unable to obtain IP address" was displayed on the screen of "Echo Show 5". So,
"Oh, maybe there's a strange child machine that's running out of IPs that DHCP gives out?"
And the router log as a trigger.
A long time ago, I didn't know that the precious experience of being forced to grab a shitty Android device with a constantly changing MAC address would be useful in a place like this.
Knowing that it would only be a child's trick, I shortened the lease time of DHCP by half by spinal cord reflex, and checked the log of NEC's optical wireless LAN router as it was. Then I got this message:
2021-07-09 00:34:57 dhcps - 0.ntc: address assigned ,192.168.1.9 ,ac:84:c6:XX:XX:XX ,LAN2021-07-09 00:35: 30 dhcps - 0.ntc: address assigned ,192.168.1.9 ,ac:84:c6:XX:XX:XX ,LAN2021-07-09 00:35:32 dhcps - 0.ntc: address assigned ,192.168.1.9 ,ac :84:c6:XX:XX:XX ,LAN2021-07-09 00:36:18 wless -17.ntc: Authentication request received, STA ac:84:c6:XX:XX:XX2021-07-09 00:36 :18 wless -18.ntc: Authentication succeeded, STA ac:84:c6:XX:XX:XX2021-07-09 00:36:18 wless -17.ntc: Authentication request received, STA ac:84:c6:XX :XX:XX2021-07-09 00:36:18 wless -18.ntc: Authentication succeeded, STA ac:84:c6:XX:XX:XX2021-07-09 00:36:18 wless - 0.ntc: Association request received, STA ac:84:c6:XX:XX:XX2021-07-09 00:36:18 wless - 1.ntc: Association succeeded, STA ac:84:c6:XX:XX:XX2021-07-09 00 :36:19 wless - 3.ntc: Disassociation request received, STA ac:84:c6:XX:XX:XX2021-07-09 00:36:19 wless -20.ntc: Deauthentication request received, STA ac:84: c6:XX:XX:XX2021-07-09 00:36:19 wless -20.ntc: Deauthentication request received, STA ac:84:c6:XX:XX:XX2021-07-09 00:36:21 wless -17 .ntc: Authentication request received, STA ac:84:c6:XX:XX:XX2021-07-09 00:36:21 wless -18.ntc: Authentication succeeded, STA ac:84:c6:XX:XX:XX2021- 07-09 00:36:21 wless - 0.ntc: Association request received, STA ac:84:c6:XX:XX:XX2021-07-09 00:36:21 wless - 1.ntc: Association succeeded, STA ac :84:c6:XX:XX:XX2021-07-09 00:36:21 wless -11.ntc: PTK 4-way handshake completed, STA ac:84:c6:XX:XX:XX2021-07-09 00: 36:32 dhcps - 0.ntc: address assigned ,192.168.1.9 ,ac:84:c6:XX:XX:XX ,LANCode language: CSS (css)Somehow, it turns out that a certain device is repeatedly disconnecting and connecting to Wi-Fi with great momentum.
By the way, this MAC address "ac:84:c6:XX:XX:XX" is all the same device. The first 6 digits of the MAC address are the vendor code, but it sounds like a TP-Link product, bingo.
As soon as I checked the TP-Link smart plug "HS105" that was installed at my feet, it was exactly this MAC address.
And the polarity of the outlet is reversed!
I can't insert it as it is ↓ I inserted it through this kind of extension cord,
I tried reinserting it in the correct orientation and all the symptoms stopped like a lie.
(*For those who are not familiar with the polarity of outlets, please refer to the article linked above. N poles, plugs with different widths for left and right forks, etc.)
As a result, I'm guessing that it was probably a symptom of noise or something like that, not a DHCP lease exhaustion, but for the time being, no similar logs were output to the router after that, and the symptom also occurred. It no longer reproduces.
Also, this may be purely my imagination, but it seems that the packet loss has not decreased on smartphones connected to the 5GHz band. I don't know.
That's why I learned the lesson of powering network devices with specified polarity correctly.
Well, I knew it because I saw the log, but if I hadn't seen it, I wouldn't have thought of this.