my wifi access point TP-LINK TP-WA901ND

I am employing another wifi access point (that's the device, whose name I am using here in the tittle) and a different WPA encrypted wifi network (SSID) for my neighbours, and today I thought, I should have a look at it again.

I got intrigued to do a firmware upgrade on the device, not really the latest one, but one of this year, and after rebooting

1. I noticed, the "System" LED kept blinking slowly,
2. and I also couldn't access it any more.

I feared, these 2 symptoms would be related, and that made me a little nervous.

I enforced a reset by pressing the reset button for 5 seconds, and applied the settings again, that I had applied severals months ago. Everything is fine now.

The "System" LED is still blinking slowly, but the manual doesn't handle this case and I also can't notice any real problem, that this might indicate, so I simply ignore that.

Just to make sure, that my lovely neighbours do not successfully invite anybody to my wifi network by themselves, today I enabled MAC address whitelisting on that wifi network, and I added the MAC addresses of all of their computers, that I am aware of. MAC address whitelisting is not the last security feature I apply to protect myself and my own computers. I also route their IP packages through a different VLAN on a managed switch, a Netgear FS526T, but that actually belongs into a different blog article.

Actually this device is not only a wifi access point. You can also operate it in several other modes, but right now I am not in the mood to describe that.