[Dnsmasq-discuss] Shut down caused by device request address.

[john doe]

On 2/22/26 12:45 PM, Matthias Andree via Dnsmasq-discuss wrote:
> 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?
> 

Newer phones have, per default, random MAC turned on, if you  want to 
assign a static lease to your phone you might want to stop that from 
happening.

-- 
John Doe