Lovely - Thank you
On 19 August 2018 at 22:46, Justin Pryzby <pry...@telsasoft.com> wrote:
> On Sun, Aug 19, 2018 at 06:29:28PM +0200, David Ventura wrote:
> > I would like to redirect (LAN) DNS requests to a different LAN server
> > (essentially forcing a failover for DHCP clients during the main DNS
> > maintenance)
> >
> > How can I achieve this?
>
> Something like
>
> #ACTION SOURCE DEST PROTO DEST SOURCE
> ORIGINAL
> # PORT PORT(S)
> DEST
> DNAT lan dns:192.168.20.117 - - -
> 192.168.20.116
>
> I think you'd need to be sure that *all* dns queries go via the router, in
> both
> directions, which means "lan" hosts need to be on a different subnet than
> the
> DNS.
>
> If they're not, maybe you can change the subnet mask to /32 before the
> maintenance (by "before" I mean more than max DHCP lease interval before).
>
> Alternately, you could migrate DNS services to a new "high availability" IP
> (say, 192.168.20.53), which is assigned as a 2nd/virtual/alias IP
> (eth1:dns) on
> the existing interface. You'd update dhcpd.conf (and wait DHCP lease
> interval)
> for dynamic hosts, and resolv.conf for static servers. Before the
> maintenance,
> you'd ifdown eth1:dns on the active server and ifup eth1:dns on the standby
> server. pacemaker is the tool I've used which automates that process.
>
> Justin
>
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