DNS issues with Fedora Core 4

We've been running a Fedora Core 4 machine for some time, with a single
network interface eth0 and ip connected to the internet.

Recently we've added another network interface eth1 with a internal ip
(say 192.168.2.1) connected to an intranet. A day or two after, we
started seeing DNS related issues, where the DNS server (external, on
the internet) would start failing (occasionally failing to give the
correct answer on nslookup, even for common sites like yahoo.com,
google.com or alexa.net)

We've doublechecked our configurations (route, iptables, dns servers)
and are investigating from the viewpoint that the DNS outage is
unrelated to the network change we made, but I thought to run it
through Google Groups if I've overlooked something that should be
checked.

I appreciate any ideas or suggestions you might have.

Thanks!

On 30 Nov 2006, in the Usenet newsgroup comp.os.linux.networking, in article
<(E-Mail Removed) om>, fuzzybr80 wrote:

>Recently we've added another network interface eth1 with a internal ip
>(say 192.168.2.1) connected to an intranet. A day or two after, we
>started seeing DNS related issues, where the DNS server (external, on
>the internet) would start failing (occasionally failing to give the
>correct answer on nslookup, even for common sites like yahoo.com,
>google.com or alexa.net)

When in doubt, the first place to look is on the wires. Run a packet
sniffer such as 'tcpdump' or 'ethereal' or 'wireshark' and see what the
DNS queries look like. Remember that the resolver will believe the first
response it receives to a query - even if that answer is "I don't know".
If it gets ANY response, it will not ask _other_ name servers.

Old guy