Raspberry Pi DHCP & Pihole

[AZ Pete]

All,
I ran into an interesting bug that I thought I'd share here. I set up one of my Raspberry Pi computers as a Pi-hole and also configured it to act as my DHCP server.
After the Pi was acting as a my DHCP router I noticed hundreds of log entries in the pihole.log file.
The Pi was being flooded with these kind of requests:

10:17:10 dnsmasq-dhcp[20546]: DHCPINFORM(eth0) 192.168.1.41 dc:a6:32:65:89:d9
10:17:10 dnsmasq-dhcp[20546]: DHCPACK(eth0) 192.168.1.41 dc:a6:32:65:89:d9 desertpi

Literally dozens of entries per second. As it turns out, I set my other two PIs to static IP addresses using the GUI interface, which put this into dhcpcd.conf file:
     interface eth0
     inform 192.168.1.41
     static routers=192.168.1.1
     static domain_name_servers=192.168.1.1

When I changed it to this there were no more log entries as listed above (i.e. changed 'inform' to 'static')
         interface eth0
         static ip_address=192.168.1.41/24
         static routers=192.168.1.1
         static domain_name_servers=192.168.1.1

As it turns out there is a bug in dhcp that causes INFORM messages to flood the router. Since my Netgear router acted as the dhcp server previously, I never saw these entries (the netgear log must not display them). But, I had always wondered why my PI's network LED was always blinking so much....

I could only find two article discussing this:
https://raspberrypi.stackexchange.com/questions/116121/huge-syslog-filled-with-dhcpcd-lines
https://forums.raspberrypi.com/viewtopic.php?t=265516

My take away: Don't use the GUI to configure things. :)

Hope this helps someone...
Thanks,
Peter





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