Am 22.02.26 um 11:33 schrieb Colin Finnis:

I have been running dnsmasq for some time on a Raspberry PI. I had no problems until about 18 months ago when the DNS would suddenly stop working. I found these types of entries in the syslog.

Feb 21 16:14:07 pilot dnsmasq-dhcp[2061]: DHCPACK(eth0) 192.168.0.242 02:ef:dd:91:3a:f3 Wild-s-S21

Feb 21 16:14:09 pilot dnsmasq-dhcp[2061]: DHCPREQUEST(eth0) 192.168.0.242 02:ef:dd:91:3a:f3

Feb 21 16:14:09 pilot dnsmasq-dhcp[2061]: DHCPACK(eth0) 192.168.0.242 02:ef:dd:91:3a:f3 Wild-s-S21

Feb 21 16:14:09 pilot dhcpcd[377]: eth0: hardware address 02:ef:dd:91:3a:f3 claims 192.168.0.8

Feb 21 16:14:10 pilot dhcpcd[377]: eth0: hardware address 02:ef:dd:91:3a:f3 claims 192.168.0.8

Feb 21 16:14:10 pilot dhcpcd[377]: eth0: 10 second defence failed for 192.168.0.8

Feb 21 16:14:10 pilot dhcpcd[377]: eth0: deleting route to 192.168.0.0/24

Feb 21 16:14:10 pilot dhcpcd[377]: eth0: deleting default route via 192.168.0.1

Feb 21 16:14:10 pilot avahi-daemon[279]: Withdrawing address record for 192.168.0.8 on eth0.

The problem always seems to be associated with Samsung phones and appears to have started after an update to the phone around 18 months ago. I have found what purports to be a solution which requires a setting change on the phone. This is fine for my phone but visitors to my house can cause the same problem and its difficult to get them all to change before the damage is done. It dosnt always happens when the phone is brought into the house, I think it occur when the phone is close to the property and the signal is poor.

As you can see the request is made for an address and the DNS responds. The request is made a second time and immediately the device seems to take over the IP address of the DNS box. DHCPD then goes into some sort of defence mode and avahi withdraws the statically assigned address. I have tried changing the address of the DNS server in case it was just the phone using a random address but that made no difference. I cant run a network monitor on the traffic so I cant see what is happen during this event. It just sems strange behaviour for the phone to suddenly decide its going to usurp the DNS’s IP address.

Im technically savvy having worked in the IT industry for 40 years but cant work out away to either prevent this or stop it happening. The only way at the moment is to reboot the PI. Any help would be appreciated.

Colin Finnis

Colin,

you're not reporting your dnsmasq version, and what's utterly unclear to me is how the MAC address is both for Wild-s-S21 and dhcpcd? What is the setting for the Samsung phone that would prevent this? Give the phone a static address?

How come dhcpcd concludes that the shown hardware address is for 192.168.0.8 if dnsmasq handed out 192.168.0.242 for what appears to be a Samsung S21 phone?

What dhcpcd and version is it? Is there a tcpdump or tshark dump or something, possibly combined with a dhcpcd debug log, so we could see what's up? This does not *obviously* look like a dnsmasq bug.

For an approach to solving this, outside dnsmasq, I wouldn't configure "pilot" (the RPi) through DHCP but give it a static address instead, possibly also from 192.168.0.* but then also reducing the DHCP address pool so its static address isn't part of the pool - and avoid running dhcpcd.

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