[Dnsmasq-discuss] interface+macvlan on same network confuses dnsmasq v2.66rc2

Gui Iribarren gui at altermundi.net
Tue Nov 5 08:52:46 GMT 2013


On 10/22/2013 08:20 PM, Simon Kelley wrote:
> On 22/10/13 17:17, Gui Iribarren wrote:
>> On 10/22/2013 05:45 PM, Simon Kelley wrote:
>>> On 21/10/13 20:31, Gui Iribarren wrote:
>>>> Hello Simon!
>>

>> Then, do you think there's any chance of getting that arp trick point to
>> 'anygw'?
>
> Yes, depending on the results of the dhcp-broadcast thing.

Indeed, setting dhcp-broadcast solved (workarounded?) the issue :D

i'll do some tcpdumps, and you mentioned you'd be interested in "arp" 
output, anything else?

cheers!

>>
>> i'll try dhcp-broadcast later today
>> what would be the downsides / cons of having dhcp-broadcast permanently
>> enabled? maybe some broken clients?
>
> Just a bit more load on clients from the broadcasts. Unless your network
> is HUGE, I doubt it's noticable.
>
> Cheers,
>
> Simon.
>
>>
>> thanks a lot!
>>
>> gui
>>
>>> For an unconfigured
>>> client (ie doing DHCPDISCOVER) dnsmasq ends up knowing the MAC address
>>> of the client and its IP address, but the client _doesn't_ know that IP
>>> address, and so can't respond to a ARP request. To get round this,
>>> dnsmasq populates the ARP table on the server directly with the IP
>>> address, MAC address and interface. Then it send the OFFER packet to the
>>> IP address and the kernel knows how to route it. I think that  you
>>> "interesting" setup may be confusing this process. In the second
>>> instance, I suspect that the crucial thing that makes it work is not the
>>> presence of a lease in the lease-file, but a correct ARP-table entry
>>> from the previous activity.
>>>
>>> Certainly, a few more experiments, and looking at the output of
>>>
>>> arp -a
>>>
>>> would be instructive.
>>>
>>>
>>> Looking again - there are more clues:
>>>
>>>   ### the OFFER it's sending is a funny mix:
>>>   ### it is sent *from* br-lan MAC and IP (192.168.11.129)
>>>
>>> That may be the MAC address thing I talked about, or it may be something
>>> else. Another experiment: try setting
>>>
>>> --dhcp-broadcast
>>>
>>> and see what happens then.
>>>
>>>
>>> Cheers,
>>>
>>> Simon
>>>
>>>
>>> Cheers,
>>>
>>> Simon.
>>>
>>> _______________________________________________
>>> Dnsmasq-discuss mailing list
>>> Dnsmasq-discuss at lists.thekelleys.org.uk
>>> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
>>
>



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