Recently I faced a DNS problem in a complex setup. I had a very locked down jumphost with one public network and two internal networks and a very nazi firewall controlling what packets went in an out.
On the inside I had a linux machine running BIND, also with a firewall and a locked down setup.
On yet another host on the inside, running HP-UX, DNS resolving worked just fine.
On the jumphost it didn’t work at all.
Took me hours to figure out what was going on. I went over the firewall again and again. On both the jumphost and the DNS server. I went over the bind configuration again and again. The network setup. To no avail. All i got was
Got recursion not available from 192.168.1.79, trying next server
In the end it turned out to be due to the fact that on the linux jump server, I had a two nameserver lines
domain zensonic.dk
search zensonic.dk
nameserver 192.168.1.79
nameserver 192.168.1.80
I hadn’t bothered to setup the DNS at 192.168.1.80 and thus my linux client would not function. As soon as I removed 192.168.1.80 from /etc/resolv.conf everything was as it should be. I hope that you, reading this, saves some hours worth of debugging. If you do, drop me a line/mail/beer 
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