Multiple rpi3 gone offlien on the lan at the same minute definitively

[matteoraggi]

Sunday 24 november at 6.24 am (Rome timezone) multiple raspberry pi 3 model b (and raspberry pi 4 too)with raspbian buster installed and dhcp configured on the lan are gone offline at the same minute then they stopped to works forever on lan and still works on wifi instead.
It is not a hardware issue, because if I change the microsd with a fresh raspbian it works well.
I made a scan with clamav and I found nothing sospicious.
The devices was all configured withotu a firewall installed, without fail2ban and user PI and a password mediam safe and one of them with a high secure password..
All with the door ssh 22 opened, and sudo not forced to ask for the password.

What could I do to discover from where this issue came from?

[swampdog]

I would check the dhcp lease first.

Code: Select all

$ sudo cat /var/log/syslog | egrep -i dhcp

..possibly "syslog.1" or older files. Also check your dhcp server logs - as everything went wrong at the same time it was probably that which caused the problem.

For example, when my ISP does a firmware update on our cable modem sometimes everything goes wrong. It's for this reason I use my own dhcp/dns server.

[pcmanbob]

As they all failed at the same time I would look at the common denominator, which in this case is your router.

its not unknown for routers to lock up and not provide IP addresses to devices connected via the wired LAN because they think they are still connected, this often happens if there is a power brown out ( low volts but not total failure ).

the first thing I would suggest is to power down all the pi's and other devices connected to the router and power cycle the router ( switch of and then back on after 30 seconds ).

your may find this will solve the problem.

If that does not solve the problem then you might be looking at corrupted SD cards especially as you say a fresh SD card allows your pi to connect to the wired LAN, but you have been very unlucky if all of them failed at the same time , but again power problems may be the route cause.

[matteoraggi]

Here attached you cna find photo of the log before and after the crash that happened at 6.24 am minute first or less..

WhatsApp Image 2019-11-28 at 09.40.20.jpeg (215.23 KiB) Viewed 270 times