interesting iptables results that make no sense

[Casey Boone <caseyboone@gmail.com>]

ok on my firewall i have a normal fd3 installation with redhat's
default iptables script plus a couple of minor modifications (most of
which make the security extremely lax for the intranet side of the
firewall).

i was doing a postrouting masq of my intranet ips but didnt have
anything set up for the forward chain except redhat's default of deny
with message.

i could ping ip addresses, ssh, do whatever as long as i did it by ip
(this coming from a box behind the firewall).  i could not dns resolve
to save myself but other udp traffic seemed to work ok (testing with
traceroute).

when i added in a forward chain for my intranet ips into the firewall
then all of a sudden dns resolving worked fine.

i see nothing in redhat's default script that deals with dns so i have
no idea why i wasnt getting more of an "all or nothing" situation
instead of all working except dns.  as best i can tell i should have
had a forward chain rule in order for the masq to work at all.

i dont get it

but now that i have the forward chain all is peachy.

Casey

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