[Dnsmasq-discuss] dnsmasq + dhclient + vpnc = DNS falls over

[Simon Kelley]

On 11/01/12 06:43, Ashton Fagg wrote:
> Hi all.
>
> I'm currently having a weird problem with an embedded PC. The machine is
> running Voyage Linux 0.5 (quite an old version, based on Debian Etch).
> Currently it's running dnsmasq version 2.35 (unfortunately no real way
> to get a new version running, sorry).
>
> The machine is set up to connect back to our LAN using VPNC. When the
> VPN is disconnected and it's merely just plugged into our LAN in the
> office, dhclient is set up to prepend 127.0.0.1 to the list of DNS
> servers. Looking at /etc/resolv.conf reveals this, 127.0.0.1 with the
> two nameservers which come in via DHCP. When the VPN is connected,
> /etc/resolv.conf gets modified by vpnc to show the DNS servers allocated
> on the tunnel interface.
>
> The issue is that eventually (and we think this has something to do with
> the dhcp lease renewing) the DNS completely falls over and fails to
> resolve anything, with only a reboot bringing it back. I'm not sure if
> this is dnsmasq, vpnc, dhclient or some combination thereof and have no
> idea where to start troubleshooting.
>
> Any help would be greatly appreciated.
>

Start by turning on logging of DNS queries in dnsmasq, that will give 
you a better idea of what is happening when it all goes wrong. Just add

log-queries

to /etc/dnsmasq.conf


HTH

Simon.