strange behavior of bind

[john doe]

Hi there,

i have a problem with my bind (9.2.3) I want to run bind in two
instances of one maschine(ext-DNS and int-DNS). I`ve already
configured bind. And it works fine for each config-file.
I bound the one DNS-instance on an Address xxx.xxx.xxx.152 the other
on xxx.xxx.xxx.172. If i start one or the other, all works fine. I can
querry local Addresses/Domains and non-local Addresses/Domains. But
when i start them both, they`re acting strange. I can querry local
Addresses/Domains on both of them, but only one of them answers
querries for non-local Addresses/Domains such as cisco.com. Both have
their forwarders. It is allways the second started instance of bind
that works fine. If i start xxx.xxx.xxx.152 and then xxx.xxx.xxx.171
then xxx.xxx.xxx.172 works fine, the other one gets timeouts. If i
start at first xxx.xxx.xxx.171 and in second xxx.xxx.xxx.152 then
xxx.xxx.xxx.152 works fine. If i stop one of them the other one works
fine.
If i make a netstat -ln ig goth the following lines:

tcp        0      0 xxx.xxx.xxx.152:53        0.0.0.0:*              
LISTEN
tcp        0      0 xxx.xxx.xxx.171:53        0.0.0.0:*              
LISTEN
udp        0      0 xxx.xxx.xxx.152:53        0.0.0.0:*
udp        0      0 xxx.xxx.xxx.171:53        0.0.0.0:*

which is Ok i guess, but i also get this line, which maybe causes the
problem:

udp        0      0 0.0.0.0:53              0.0.0.0:*

Why is the Port 53 bound to udp 0.0.0.0? In the named-int.conf i
define:
listen-on port 53 { xxx.xxx.xxx.152; }; 
similar in the named-ext.conf:
listen-on port 53 { xxx.xxx.xxx.171; }; 

I hope somebody can help me. And please forgive my poor english. 

Torsten