My RPi pihole was just working fine a couple hours ago. However recently I had to restart my RPi because it was having problems connecting to the Google API I had it connected to (use it as a voice AIY Kit + PiHole). After reboot, the RPI seems to have problems with the DNS and I cannot ping website names, but I can ping IP addresses like ping 8.8.8.8 just fine.
Expected Behaviour:
ping google.com should return a response
Actual Behaviour:
ping google.com returns Temporary failure in name resolution ping 8.8.8.8 works normally as expected and I get responses
Debug Token:
Router information
I am using TomatoUSB firmware (Shibby version) on my router, and I saw this similar topic and I checked to confirm I did not check off "Intercept DNS port (UDP 53)" in my Advanced > DHCP/DNS settings.
I also checked to make sure I did not have any iptable rules or firewall exceptions and in my router and on my RPi. I do not have any firewall settings blocking ports 53 or 80 as far as I know. iptables -L on my RPi is empty. In my router, Adminitrations > Scripts is empty.
Strange, after fiddling around with the RPI settings, DNS, iptables, and Google AIY kit configs, I tried the following sequence of steps, and now everything is working. Not sure if there was an update for RPi that fixed it but here is what I did and now its back to working just fine. Still don't know what the root cause of it was, but here is what I did for anyone who may have something similar.
Edit /etc/resolv.conf file and changed nameserver 127.0.0.1 to nameserver 1.1.1.1 just to get a connection working temporarily
Confirmed the DNS was fixed by running ping google.com and getting a response
Ran sudo apt-get update
Re-ran ping google to make sure nothing broke and checked to see if the Pihole admin interface was still working and all green in the top left
Restarted the RPi: sudo reboot
PiHole and RPi working perfect and no more "Temporary failure in name resolution" when I ran ping google.com. The file resolv.conf is back to its default 127.0.0.1 upon reboot.