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Old 05-24-2003, 01:21 PM   #1
Registered: May 2003
Posts: 168

Rep: Reputation: 30
iptables help

Hi i am new to linux and am having trouble setting up my iptables.

I want to host my own web server and mail server.

I would like to know what changes need to be made to iptables to allow
web and mail to come through. The reason why i think it is my
firewall is because i can send mail out but i cannot receive mail. I
can view the web and i can view my web page locally but i cannot
access it from the internet.

I get an unknown host error when i try to reply to a mail message. I can also view my web page from the server but not from another machine on the lan. When i try from another machine on the lan it comes up with the username and password for the adsl modem/router. From the internet, the error i receive is "this page cannot be displayed".

This is what i have added to iptables by typing from a terminal

iptables -A INPUT -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -p tcp --dport 25 -j ACCEPT

Do i need to add anything else?

I have an adsl router which has an internal ip address and an external
ip address allocated to it by the isp. Then my server runs off the
switch and is not directly attached to the router.

Do i need to add the following lines?

"iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j DNAT --to
internal ip address" and do the same for port 25?

How do i get the external ip address to be forwarded to the router and
then to the internal ip address of my machine?

I have a dynalink adsl router, one port. i have added the following
nat commands to open up ports 80 and 25. "inbound add 80/tcp internal
ip address - add a rule" and "inbound add 25/tcp internal ip address -
add a rule"

Any ideas anyone?
Old 05-24-2003, 02:07 PM   #2
Registered: Feb 2002
Location: Fairfax, VA
Distribution: RedHat 8, Mandrake9.1, Slack9
Posts: 456

Rep: Reputation: 31
you need to masquerade your connection for the internal network. and if you are running the server on a local machine you need to do port forwarding.

the bset thing to do would be get a GUI firewall wrapper and then configure it systematically.

there are some good firewall wrappers

firestarter, fwbuilder, guarddog


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