[Dnsmasq-discuss] Linux and MacOS cannot get DHCP address

[Simon Kelley]

Chris Blake wrote:
> Greetings community,
> 
> I have done a brief search through the archives and cannot find any
> answers, perhaps I have overlooked something.
> 
> On our network all our Windows hosts do not have any issues getting a
> DHCP address from dnsmasq, but Ubuntu machines and MacOS do not.
> 
> My dnsmasq log file tails as follows while my Ubuntu desktop is trying
> to connect :
> 
> Feb  2 12:46:39 dnsmasq[4831]: DHCPDISCOVER(eth0) 192.168.2.100
> 00:1f:e2:5a:aa:fa
> Feb  2 12:46:39 dnsmasq[4831]: DHCPOFFER(eth0) 192.168.2.147 00:1f:e2:5a:aa:fa
> Feb  2 12:46:39 dnsmasq[4831]: requested options: 1:netmask,
> 28:broadcast, 2:time-offset, 3:router,
> Feb  2 12:46:39 dnsmasq[4831]: requested options: 15:domain-name,
> 6:dns-server, 119:domain-search,
> Feb  2 12:46:39 dnsmasq[4831]: requested options: 12:hostname,
> 44:netbios-ns, 47:netbios-scope,
> Feb  2 12:46:39 dnsmasq[4831]: requested options: 26:mtu,
> 121:classless-static-route, 42:ntp-server
> Feb  2 12:46:39 dnsmasq[4831]: tags: known
> Feb  2 12:46:39 dnsmasq[4831]: sent size:  1 option: 53:message-type  02
> Feb  2 12:46:39 dnsmasq[4831]: sent size:  4 option:
> 54:server-identifier  c0:a8:02:de
> Feb  2 12:46:39 dnsmasq[4831]: sent size:  4 option: 51:lease-time  00:00:a8:c0
> Feb  2 12:46:39 dnsmasq[4831]: sent size:  4 option: 58:T1  00:00:54:60
> Feb  2 12:46:39 dnsmasq[4831]: sent size:  4 option: 59:T2  00:00:93:a8
> Feb  2 12:46:39 dnsmasq[4831]: sent size:  4 option:  1:netmask  ff:ff:ff:00
> Feb  2 12:46:39 dnsmasq[4831]: sent size:  4 option: 28:broadcast  c0:a8:02:ff
> Feb  2 12:46:39 dnsmasq[4831]: sent size:  4 option:  6:dns-server  c0:a8:02:de
> Feb  2 12:46:39 dnsmasq[4831]: sent size: 14 option: 15:domain-name
> 74:61:75:73:70:61:63:65:2e:6c:6f:63:61...
> Feb  2 12:46:39 dnsmasq[4831]: sent size:  4 option:  3:router  c0:a8:02:01
> Feb  2 12:46:39 dnsmasq[4831]: DHCP packet: transaction-id is 612899809
> Feb  2 12:46:39 dnsmasq[4831]: Available DHCP range: 192.168.2.101 --
> 192.168.2.150
> Feb  2 12:46:39 dnsmasq[4831]: DHCPDISCOVER(eth0) 192.168.2.100
> 00:1f:e2:5a:aa:fa
> Feb  2 12:46:39 dnsmasq[4831]: DHCPOFFER(eth0) 192.168.2.147 00:1f:e2:5a:aa:fa
> 
> If I have overlooked something in the archives please point me in the
> right direction, or possibly shed some light as to why it is only the
> Ubuntu and MacOS machines that have this issue.
> 

This smells like the exact mirror image of
http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2010q1/003575.html
the windows clients will be demanding broadcast replies, whilst the 
Linux and MacOS ones will get unicast. If you have firewall 
configuration in place that blocks the unicast replies (connection 
tracking?) then you'll see such symptoms.

As a quick check, add

dhcp-broadcast

to /etc/dnsmasq.conf to force broadcasts always. If the Linux and MacOS 
clients now work, then I'm right.


HTH


Simon.