Unable to access internet after restarting router

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1

The issue I am facing:

  • After my router automatically rebooted this morning at 03:00 AM, all devices on my network were no longer able to access any external sites.
  • I could not access my router's webpage at 192.168.0.1 from any device on the network.
  • I could access other devices on my network by their hostnames.
  • All devices on my network were getting IP addresses of 169.x.x.x, indicating that they could not contact the DHCP server.
  • FTL.log was getting flooded with these messages every second:
    WARNING in dnsmasq core: DHCP packet received on enxb827eb5bbecc which has no address
    WARNING in dnsmasq core: no address range available for DHCP request via enxb827eb5bbecc
  • pihole.log was getting flooded with this message every second:
    dnsmasq-dhcp[380]: no address range available for DHCP request via enxb827eb5bbecc
  • I was able to temporarily fix the issue by connecting to my router's webpage using a VPN I had set up on the router, which allowed me to enable the DHCP server on the router and disable it on the Pi-hole.

Details about my system:

  • Pi-hole was configured as both the DNS and DHCP server at the time.
  • Pi-hole is running on a very old Raspberry Pi Model B Rev 2.
  • The debug log I generated says that dhcp-range=192.168.0.1,192.168.0.251,24h, but that's after I changed it to try and fix the issue. This was dhcp-range=192.168.0.100,192.168.0.251,24h at the time of the issue.
  • Router is behind an AT&T modem with IP passthrough enabled, set to pass to the router by its MAC address.
  • Pi-hole is connected to the router via ethernet cable.
  • Router IP: 192.168.0.1
  • Pi-hole IP (reserved in DHCP): 192.168.0.10

What I have changed since installing Pi-hole:

  • Enabled DHCP server on my Pi-hole and disabled it on my router.
  • Standard adlist and client setup.

Help requested:

  • I'd like to re-enable the DHCP server on the Pi-hole, but I want to ensure that I won't lose my connection again after another router reboot. I probably messed up something when configuring the DHCP server. What can I check to ensure that I have DHCP set up properly on Pi-hole?

Debug log token: https://tricorder.pi-hole.net/PsNbWrWL/

2

A DHCP server can't assign an IP to itself.
Consequently, your machine hosting Pi-hole and its DHCP server lacks a proper private IP, sporting an LLA instead (as you are already aware of):

*** [ DIAGNOSING ]: Network interfaces and addresses
   2: enxb827eb5bbecc: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
       inet 169.254.41.234/16 brd 169.254.255.255 scope global noprefixroute enxb827eb5bbecc
          valid_lft forever preferred_lft forever

Since you use your Pi-hole machine as DHCP server, you'd have to define a static IP for your Pi-hole on device.

For recent Raspberry Pi OS 11 (Bullseye), as reported in your debug log, that can be done by editing /etc/dhcpcd.conf (or by configuring NetworkManager, if you opted to use that instead of dhcpcd via raspi-config).

3

If I'm reading the documentation for dhcpcd.conf correctly, I would just need to add these lines to the end of the file, correct? Should I use eth0 or enxb827eb5bbecc? Do I need to set domain_name_servers to the address of the Pi-Hole device?

interface eth0
        static ip_address=192.168.0.10/24
        static routers=192.168.0.1
        static domain_name_servers=
4

We'd usually recommend to set domain_name_servers to Pi-hole plus a public DNS resolver (e.g. 127.0.0.1 9.9.9.9) or a public DNS resolver only (if you don't need to filter your host, which is likely the case for a server), so your host still has DNS resolution even if Pi-hole would be inoperational for reasons, allowing pihole commands to try a repair on it.

The most important part is the router gateway.
You want to make sure it matches your router's IP.

5

Thank you! I'll try out this configuration and make sure I've got it set up right.

6

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