Problem with DNS through a gateway

I have a machine with dialup networking that acts as a gateway
to my small LAN. Running Fedora Core 4 everything works fine.
(or as fine as possible, considering the slow outside networking)
I put on a Fedora Core 5 test installation and used the same
iptables incantation that works for FC4. With no change to the
other machines on the LAN they can ping to a numeric IP address
through the gateway but they don't get DNS service. DNS does
work on the gateway machine under FC5. Any clues?
--

jhhaynes at earthlink dot net

> other machines on the LAN they can ping to a numeric IP address
> through the gateway but they don't get DNS service. DNS does
> work on the gateway machine under FC5. Any clues?

If I understand you correct, you wanted to provide DNS service to your
LAN. Did you have your FC5 machine's DNS configured properly? Should
you run a dhcpd on that machine, you can configure it assigning DNS
address along with IP addresses. You might like to run a cache-only
(caching only) or forwarding DNS to your ISP's DNS server over your
slow connection .

Here is an example you can count on.

http://www.zytrax.com/books/dns/ch6/

Or

You may not need a DNS server at all, should you use IP masquerading
where your LAN's machines are configured to use ISP's DNS server.


--
Raqueeb Hassan
Bangladesh

On Wed, 14 Jun 2006, in the Usenet newsgroup comp.os.linux.networking, in
article <cQYjg.5708$(E-Mail Removed). net>, Jim Haynes
wrote:

>I put on a Fedora Core 5 test installation and used the same
>iptables incantation that works for FC4. With no change to the
>other machines on the LAN they can ping to a numeric IP address
>through the gateway but they don't get DNS service. DNS does
>work on the gateway machine under FC5. Any clues?

"The other boxes" - where are they looking for DNS? Assuming a *nix O/S
on them - what's in /etc/resolv.conf? (If windoze, there's probably some
icon to click on to find out.) On the gateway box, does
'/usr/sbin/tcpdump -i eth0' show those boxes making DNS queries? To who?
On the gateway box, does '/usr/sbin/tcpdump -i ppp0' show these same
queries going out with the source address of the ppp0 interface? Do
you see DNS replies coming back in from where-ever? Did the reply get
forwarded back to the local boxes?

Old guy

In article <(E-Mail Removed). com>,
Raqueeb Hassan <(E-Mail Removed)> wrote:
>
>You may not need a DNS server at all, should you use IP masquerading
>where your LAN's machines are configured to use ISP's DNS server.
>
That is correct - it works with the FC4 gateway with IP masquerading
and the LAN machines use the ISP DNS server. It's just when I run the
gateway on FC5 that DNS fails. Thanks to Moe Trin for the suggestions
to use tcpdump and see if DNS queries are flying around on either side
of the gateway. I'll try that.
--

jhhaynes at earthlink dot net