[Dnsmasq-discuss] Dnsmasq wont recieve DHCP request messaegs

[Simon Kelley]

On 09/02/14 07:25, Kiazada Dany-GVN438 wrote:
> Hi,
>
> I’m using the program as a DHCP server for a Linux machine. The server
> needs to toggle between two different subnets, with different GW (on the
> same interface – ‘br0’), and assign an IP for a windows PC.
>
> So for example upon power up the DHCP will assign an IP to the PC
> (connected via Ethernet), with subnet ‘A’.
>
> After a while, the DHCP will need to assign a different IP, on a
> different subnet ‘B’.
> The way I implemented it is running dnsmasq on the Linux machine :
>
>   -C /etc/dnsmasq.conf/sbin/dnsmasq -d --clear-on-rel
>
> With The following  dnsmask.conf file (subnet ‘A’) :
>
> dhcp-range=27.187.20.14,27.187.20.14,255.255.255.0,3600
>
> interface=br0
>
> dhcp-option=3,27.187.20.1
>
> dhcp-option=6,27.187.20.1
>
> dhcp-leasefile=/etc/dnsmasq.leases
>
> dhcp-lease-max=253
>
> log-dhcp
>
> After I receive an indication to change the subnet, I kill the dnsmasq
> server, and run it again the same way only with the second subnet ‘B’.
> I noticed that the dnsmasq.leases is empty, and there are no connected
> clients after the second power up. The PC is sending DHCPINFORM messages
> (with no response) and
>
> In order to have the PC ask for a new IP, I cut the power to the
> Ethernet Iface. This causing the PC to send DHCPREQUEST messages (with
> no DISCOVER messages before).
> The dnsmasq is not responding to the REQUEST messages although it’s a
> broadcast message, and I can see at tcpdump that they arrive to the
> Linux machine…
>
> I can see in the app logs that the dnsmask is receiving the INFORM
> messages, but I cannot see the REQUEST messages (in the app logs).
>
> The thing is the PC remembers the first IP it was assigned (subnet ‘A’),
>   and although the DHCP server has a different IP range configuration,
> the PC is still showing the old IP.
>
> So my goal is to have the PC assigned a new IP (without any PC
> involvement, meaning no ipconfig renew\release commands). from a
> different pool, different subnet and GW, after the dnsmasq is restarted.
>

Try adding

dhcp-authoritative

to your configuration.


Cheers,

Simon.