I have a Raspberry Pi 4 that I use as a PiHole server for my home network (which I can’t recommend enough doing). It has been running for a while now, but after the last updates it was not booting anymore. I checked the (arguably pretty cheap) MicroSD card that I used and it was dead. So, I decided to get a new one and set up the PiHole server again - since I was pretty sure that I did not need to configure a lot.
However, after installing Raspbian Lite via the Raspberry Pi Imager and booting the Pi, I noticed that the network LEDs on the Pi turned off periodically.
Like, they were blinking (indicating activity) for 1-2 seconds and then turn off for 1-2 seconds.
I also got a host of networking issues inside the Pi, like ping not working, apt-get not working, DNS resolution failures, etc..
After tons of research, trial-and-error and frustration, multiple re-imaging-procedures and different cables, I found a solution that worked for me - so I need to note it down for my future self 😄
This post on the Raspberry Pi forums was the key to my solution.
I ran the suggested command journalctl -b to look through the system logs and found a lot of occurrences of messages indicating eth0 being connected and then down again 2 lines afterwards.
Then I used sudo nano /boot/firmware/config.txt (the path mentioned on the forums has changed to this one) and added the following line near the beginning of the file:
dtparam=eee=off
Apparently, the issue was related to the Ethernet Energy Efficient (EEE) feature that was enabled by default. Deactivating it like this fixed all of my networking issues and the PiHole server is running smoothly again.