4 interfaces, 4 different responses, 2 forwardings and 1 cache. How ?

[Jan Vicherek]

  Hi,

  I have 4 interfaces(lo, eth0, eth1, ppp0), two of them going to the
Net(ppp0, eth1). I have about 10+1 domains to take care of; 1 my domain,
for which I also do reverse resolution (+1) on LAN, and then the remaining
9 just for virtual hostings.

 While resolving the names->addresses, I want to generate four different
responses, each for the interface on which the request came. so I figured
I need to run 4 'named' daemons. Right ?

 Now the two on ppp0 and eth1 should only resolve those 10 domains, no
other requests should be resolvable. Do I accomplish that by supplying
null "forwarders" list ? How do I make sure that no cache is being
maintained and no external DNS servers are contacted to resolve the
incoming requests ? I guess that's a newbie question and I guess the
answer is "Don't specify any forwarders, dummy^H^H^H^H^H^H newbie!"

 I want requests that come on lo and eth0 for those 10+1 domains resolved
localy, but all other requests (outside those 10+1 domains) should be
resolved using some of four external DNS servers (I was given two on ppp0
and two on eth1). But if a request gets resolved externaly by forwarding,
it is cached (right?). So I only want one cache for the two interfaces (lo
and eth0). How do I setup these ?

 How do I make sure that the named bound to eth0(LAN) will not keep any
growing cache ? (Since I do have to specify a forwarder.)

 [ But instead asks the named bound to lo(loopback) to use its cache to
resolve requests that come to eth0 that are outside those 10+1 zones. ]

 Would the following configuration do it ? :

/etc/named.conf.lo :
options { forwarders { ext_dns1; ext_dns2; }; listen-on { 127.0.0.1; }; };
zone "." { type hint; file "named.ca"; };
zone "0.0.127.in-addr.arpa"      { type master; file "named.local"; };
/* now 10x */ zone "a_domain."   { type master; file "...lo"; };
zone    "4.168.192.in-addr.arpa" { type master; file "...lo"; };

/etc/named.conf.eth0
options { forwarders { 127.0.0.1; }; listen-on { 192.168.4.1; }; };
// now 10x zone "a_domain."      { type master; file "...eth0"; };
// zone "4.168.192.in-addr.arpa" { type master; file "...eth0"; };

/etc/named.conf.ppp0
options { listen-on { 1.2.3.4; }; };
// now 10x zone "a_domain." { type master; file "...ppp0"; };

/etc/named.conf.eth1
options { listen-on { 2.3.4.5; }; };
// now 10x zone "a_domain." { type master; file "...eth1"; };


   Thanx,

        Jan