[Dnsmasq-discuss] DNSmasq Forward DNS on Multiple Interfaces

Petr Menšík pemensik at redhat.com
Thu Sep 24 09:00:51 BST 2020


Do you have the same IP addresses on those interfaces?

anyway, it seems to be implemented already. Check --server in man
dnsmasq(8).

--server=10.1.2.3 at ethX

I am not sure it just uses source IP address from that interface or it
can differentiate the same IP addresses on different interfaces. Please
try and share results.

On 9/23/20 11:16 PM, Hooman wrote:
> Hi Petr,
> 
> Thank you for your response. I am actually looking for a way to forward
> packets to a specific interface. The DNS servers on all these interfaces
> are the same, so I can't use the method you mentioned in your response.
> 
> I am looking for something similar to the `ping -I interface` option [1]
> that sets the source IP address (or interface) for the ping packets.
> 
> Thank you,
> 
> -H
> 
> 
> [1] https://linux.die.net/man/8/ping
> 
> On 9/23/20 2:47 PM, Petr Menšík wrote:
>> Hi,
>>
>> I doubt there is simple way to forward to "interface". DNS queries needs
>> target IP to forward to. You would need
>> dnsmasq ...  --no-resolv --server=<ethX forwarder IP>
>>
>> I just guess you want to use DNS server configured by DHCP on given
>> ethernet interface. I doubt it is possible to integrate directly into
>> dnsmasq. It is not DHCP client, but DHCP server. You would have to find
>> a way to obtain DNS settings for given interface and prepare
>> configuration snippet for dnsmasq.
>>
>> With fixed IP addresses, it would be much easier :), just use different
>> --server on each instance.
>>
>> Cheers,
>> Petr
>>
>> On 9/23/20 8:13 PM, Hooman wrote:
>>> Hi,
>>>
>>> I am using `hostapd` to setup WiFi hotspot networks on my Ubuntu 18.04.
>>> I am using [this guide][1] to setup multiple SSIDs on my WiFi interface.
>>> And to enable DHCP on the hotspot networks, I use `dnsmasq`.
>>>
>>> I run a separate instance of `dnsmasq` for each SSID. Now, I have
>>> multiple Ethernet interfaces available on this computer and I want each
>>> `dnsmasq` instance to forward the DNS requests it receives on a
>>> different Ethernet interface.
>>>
>>> Is there an easy way to do this? In other words, is there a way to tell
>>> `dnsmasq` which Ethernet interface to use for forwarding DNS queries? I
>>> know that in theory I can use network namespaces to do this, but I'm
>>> looking for an easier way.
>>>  
>>> Thank you!
>>>
>>> -H
>>>
>>>
>>> [1]: http://wiki.stocksy.co.uk/wiki/Multiple_SSIDs_with_hostapd
>>>
>>>
>>> _______________________________________________
>>> Dnsmasq-discuss mailing list
>>> Dnsmasq-discuss at lists.thekelleys.org.uk
>>> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
>>>
> 

-- 
Petr Menšík
Software Engineer
Red Hat, http://www.redhat.com/
email: pemensik at redhat.com
PGP: DFCF908DB7C87E8E529925BC4931CA5B6C9FC5CB

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