[Dnsmasq-discuss] Client DHCP Configuration Question

[john doe]

On 7/20/25 4:34 PM, Simon Kelley wrote:
> 
> 
> On 7/17/25 19:53, bad.cow5843 at fastmail.com wrote:
>> Dear dnsmasq people,
>>
>> This is not a problem with dnsmasq itself, but I don't know where else 
>> to ask, so I am going ahead and I apologise in advance of it's off-topic.
>>
>> I have been using dnsmasq for months with various clients and had no 
>> trouble at all, until I tried a Debian client. The problem I have is 
>> that the client attaches to two networks automatically: a wired one 
>> which is connected to my dnsmasq server, and a wifi connection to a 
>> router which is on another private subnet which is NOT routed by my 
>> server. But when both interfaces are up the client tries to use the 
>> wrong DNS server. It's the wrong one because it's not on the subnet my 
>> server is routing. If only one of either of the Debian client's 
>> interfaces is up it works fine.
>>

Do you realy need both interface connected at the same time?

>> So, is there anything I could potentially do in the dnsmasq 
>> configuration to stop this behaviour? Is it even the right behaviour? 

As Simon said, the easyest way is to not send dns information to 
specific clients.

You could also force the DNS to be used on the client.
Generally speaking, having DNS from multiple subnets is not realy an issue.

In other words, why do you need to ask for help.

>> Maybe I should try raise it as a bug against Debian, but I am not sure 
>> about this.
>>
>> Apologies again if this is off-topic, just ignore it and be thankful 
>> that I didn't put my questions in a zip file! :-)
>>
> 
> 
> The source of the problem is the wifi router. Can you change its 
> configuration so that it doesn't advertise a DNS server which doesn't work?
> 
> Cheers,
> Simon.
>> Ian
>>
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> 
> 
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-- 
John Doe