"No address range available for DHCPv6 request via eth0" dnsmasq warning due to old prefix

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1

I have a Pi Zero, running Pi-hole with IPv4 and IPv6 DHCP active, and with IPv6 stable-privacy and prefer temporary IP options set.

After one day of uptime, it starts to generate dnsmasq warnings that there is:
no address range available for DHCPv6 request via eth0

There is definitely a valid IPv6 prefix, but Pi-hole thinks that it's an old prefix.

Nov 6 16:48:09 dnsmasq-dhcp[595]: router advertisement on 2001:4479:5703:a100::, old prefix for eth0
Nov 6 16:48:10 dnsmasq-dhcp[595]: RTR-ADVERT(eth0) 2001:4479:5703:a100:: old prefix

Is this an OS or Pi-hole problem, and is there a solution to these warnings?

Note that I know I can suppress the warnings via the configuration, but I'd prefer to eliminate the warnings, if possible.

2

Please upload a debug log and post just the token URL that is generated after the log is uploaded by running the following command from the Pi-hole host terminal:

pihole -d

or if you run your Pi-hole as a Docker container:

docker exec -it <pihole-container-name-or-id> pihole -d

where you substitute <pihole-container-name-or-id> as required.

3

pxzC9xFH

Perhaps post sudo pihole -d for those of us who don't do this all the time.

4

Thank's for the heads up, I'll update the template for that sudo.

That's just pihole-FTL/dnsmasq reporting that the prefix hasn't changed.

You see that message because your Pi-hole isn't configured to provide Stateful DHCPv6 services, i.e. it doesn't assign IPv6 addresses to clients.

Most OSs will prefer to acquire their IPv6 addresses via NDP/SLAAC anyway, combining interface IDs they compute for themselves with IPv6 prefixes as advertised by your router.

The message will disappear if you untick Enable additional IPv6 support (SLAAC + RA) in Pi-hole's DHCP Settings.

Unrelated to your observation, your debug log shows that you have customised your Pi-hole's DHCP server to distribute a public DNS server along with Pi-hole:

     dnsmasq_lines = [
       "#DHCPv6",
       "dhcp-range=::,constructor:eth0,ra-names,ra-stateless,64",
       "#DNS Servers",
       "dhcp-option=option:dns-server,192.168.231.154,1.1.1.2",
       "dhcp-option=option6:dns-server,[fe80::24af:9b8b:1d92:626b],[2606:4700:4700::1112]"
     ] ### CHANGED, default = []

This would allow clients to by-pass Pi-hole via Cloudflared's DNS servers at their own discretion.
Pi-hole has to be the sole DNS server for your network.
You should remove that public DNS server.

5

Okay, but why is it expecting that it would have changed and reporting that it hasn't changed so frequently (every 1+ seconds), but only after one day of operation?

If that option is unnecessary, why does it exist in the Basic DHCP settings?
My understanding of that option, is that the Pi-hole is not advertising that it can provide Stateful addresses. It's advertising the IPv6 prefix and DNS servers, but telling devices to create SLAAC addresses.

I've already explained how that works, to you.

6

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