Simple INPUT chain question.

[Joel Fressa]

Today, I tried to ACCEPT only TCP/UDP port 21,23,53 and 80 to the
INPUT chains thinking that would allow only packets on those ports
to my firewall PC and allow those ports to be forwarded to the various
workstations on the LAN. Didnt work. Blocked my LAN workstations
altogether.

What did I do wrong? How can I just allow ports 21,23,53 and 80 to
the firewall / internet gateway and disallow traffic like that to my
LAN. My LAN doesnt need to access port 80 because it goes
through my firewall / gateway PC. Right?

Thanks!

Joel

PS: IPTABLES is hard as hell to figure out, it would be nice to have some
really good documents. Something with Syntax that is up to date,
examples that actually work and some simple english as to how it
conceptually
works. ;-)