No connectivity for IPv4 devices while IPv6 works

[Xiaopang]

Expected Behaviour:

IPv4 requests should be processed by Pi-hole.

Actual Behaviour:

Devices that don't support IPv6 get connected to WiFi, but without internet connectivity. Only when I remove Raspi as DNS-server does it work for them. Raspi has IPv4 assigned, but neither can be pinged from any device on the network (time out), nor can ping other IPv4 addresses on the network. IPv6 pings work fine.

IPv4 has been configured on Raspi and I can see it being assigned both on Raspi as well as on the router's end. No firewall is active. There is no client isolation in router (Fritz Box 6390) active. Pi-hole has been installed on a standard installation on Raspi OS 11 (Bullseye). I've been doing this kind of installation in the past on multiple Raspis without any problems so far, but now I'm at my wit's end.

Pi-hole's query log only contains IPv6 client names, but it could be that this is an underlying configuration problem of Raspi OS as I can't even SSH into the device via IPv4, but have to rely on IPv6.

Debug Token:

Log contents removed by moderator.

[jfb]

@Xiaopang

Debug Token:

This is not the token, it is the log output. I have removed the log contents and made them private for the moderators, to protect your privacy.

[Xiaopang]

Thank you.

[Xiaopang]

I managed to solve it. The reason for this issue was the Raspi having a static IP address assigned while my router's DHCP server was still active. However, the static IP equaled the DHCP-server's IP, plus the server was set to never change it for that device, so I'm still stumped about this issue.

Anyway, after deactivating the router's DHCP-server and activating the one built into Pihole, everything now works: IPv4-based devices are connected to the internet and pinging/sshing the raspi via IPv4 works as well.