[Dnsmasq-discuss] No DHCP leases handed on bridge interface

Albert ARIBAUD albert.aribaud at free.fr
Fri Jul 15 21:10:03 BST 2016

Bonsoir Seb,

Le Fri, 15 Jul 2016 17:09:02 +0000 (UTC)
Sébastien Delafond <seb at debian.org> a écrit:

> On 2016-07-15, Albert ARIBAUD <albert.aribaud at free.fr> wrote:
> > OTOH, there *is* a link with the networking setup since dnsmasq
> > works without the bridge and stops working with the bridge.  
> True.
> > Also, the fact tha ISC dhcp works might hinge on how ISC dhcp
> > listens to requests exactly vs. how dnsmasq does. What's the ISC
> > dhcp config exactly?  
> The shorted functional one is:
>   subnet netmask {
>     range;
>   }

No mention of the interfaces it binds to and how? No functional
equivalent to the interface-related options of dnsmasq?

> > Speaking of tcpdump, can you use it to capture a successful request
> > to ISC dhcp and a (failed) request to dnsmasq, on eth0.2 as well as
> > on br.eth0-2, and make the captures files available somewhere?  
> They're now at https://people.debian.org/~seb/dnsmasq-pcaps

Thanks. The captures are identical except for obvious differences like
transaction numbers or checksums, which have no influence on acceptance
or rejection of a DHCP request.

Which seems to imply that dnsmasq makes the difference based on the
interface it receives the request on -- hence my asking how ISC dhcp
chooses the interfaces it listens to... and how dnsmasq does it.

You might want to check whether the bridge is brought up before or
after dnsmasq is started. Also, try combinations of interface= and
bind-interfaces. Also, checkout bridge-interface= if it is available in
your version of dnsmasq.

> Cheers,
> --Seb


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