[Dnsmasq-discuss] server-side dynamic resolving

[John Hallam]

On Mon, Aug 13, 2012 at 05:17:49PM +0200, Chris Wilson wrote:

> Running a real DNS server and dnsmasq on the same host might be
> tricky. You might need to add an IP alias on the server and bind
> bind to that alias, and dnsmasq's DNS server to the main IP address.

  I routinely run 2-3 DNS servers (tinydns) and 2 caches (dnscache and
dnsmasq) on my main server machines*, without problems.  The trick is
to set up a space of addresses on the lo interface that the different
servers can use.

  For example, allocate 127.0.53.1 .. 127.0.53.n to any authoritative
DNS servers you need to run;  127.0.53.254 for dnscache and
127.0.53.253 for dnsmasq DNS service, and all works as you'd hope,
assuming that you point the caches at the correct servers.

  (Note:  this only works for traffic internal to the box.  If you
need external traffic too, then at least some of these addresses must
be "real" in the sense of not-loopback -- because the kernel silently
discards addresses outside 127.0.0.0/8 on the lo interface and such
addresses are not routable and not NAT-able either.)

Cheers,

	John

* If you are wondering, why two caches, the reason is that dnsmasq
allows me to redirect troublemaker domains to the black hole easily,
while dnscache is a somewhat-paranoid full recursive caching
resolver.  (The dnsmasq has to forward queries to the dnscache;  the
reverse doesn't work straightforwardly.)